How many classes can a single .NET DLL contain ?
A: It can contain many classes.
True or False: To test a Web service you must create a windows application or Web application to consume this service ?
A: False, the webservice comes with a test page and it provides HTTP-GET method to test.
Which control would you use if you needed to make sure the values in two different controls matched ?
A: CompareValidator Control
Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box ?
A: DataTextField property
What does WSDL stand for ?
A: (Web Services Description Language)
True or False: A Web service can only be written in .NET ?
A: False
What tag do you use to add a hyperlink column to the DataGrid ?
A:
What tags do you need to add within the asp:datagrid tags to bind columns manually ?
A: Set AutoGenerateColumns Property to false on the datagrid tag
What base class do all Web Forms inherit from ?
A: The Page class.
What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control ?
A: You must set the DataSource property and call the DataBind method
Which template must you provide, in order to display data in a Repeater control ?
A: ItemTemplate
If I’m developing an application that must accommodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing) what would be the best approach to maintain login-in state for the users ?
A: Maintain the login state security through a database.
What does the “EnableViewState” property do? Why would I want it on or off ?
A: It enables the viewstate on the page. It allows the page to save the users input on a form.
Suppose you want a certain ASP.NET function executed on MouseOver overa certain button. Where do you add an event handler ?
A: t’s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add(”onMouseOver”,”someClientCode();”)
What’s a bubbled event ?
A: When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.
What’s the difference between Codebehind=”MyCode.aspx.cs” andSrc=”MyCode.aspx.cs” ?
A: CodeBehind is relevant to Visual Studio.NET only.
Where do you store the information about the user’s locale ?
A: System.Web.UI.Page.Culture
Where does the Web page belong in the .NET Framework class hierarchy ?
A: System.Web.UI.Page
What’s the difference between Response.Write() andResponse.Output.Write() ?
A: The latter one allows you to write formattedoutput.
Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process ?
A: inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension),the ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker process aspnet_wp.exe.
What is method to get XML and schema from Dataset ?
getXML () and get Schema ()
Differences between dataset.clone and dataset.copy ?
A: Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data.
Copy - Copies both the structure and data for this DataSet.
How to check if a datareader is closed or opened ?
A: IsClosed()
In how many ways we can retrieve table records count? How to find the count of records in a dataset ?
A: foreach(DataTable thisTable in myDataSet.Tables){
// For each row, print the values of each column.
foreach(DataRow myRow in thisTable.Rows){
What happens when we issue Dataset.ReadXml command ?
A: Reads XML schema and data into the DataSet.
Explain different methods and Properties of DataReader which you have used in your project ?
A: Read
GetString
GetInt32
while (myReader.Read())
Console.WriteLine(”\t{0}\t{1}”, myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
Difference between DataReader and DataAdapter / DataSet and DataAdapter?
A: You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the DataReader can increase application performance and reduce system overhead because only one row at a time is ever in memory.
After creating an instance of the Command object, you create a DataReader by calling Command.ExecuteReader to retrieve rows from a data source, as shown in the following example.
SqlDataReader myReader = myCommand.ExecuteReader();
You use the Read method of the DataReader object to obtain a row from the results of the query.
while (myReader.Read())
Console.WriteLine(”\t{0}\t{1}”, myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
The DataSet is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source. It can be used with multiple and differing data sources, used with XML data, or used to manage data local to the application. The DataSet represents a complete set of data including related tables, constraints, and relationships among the tables. The methods and objects in a DataSet are consistent with those in the relational database model. The DataSet can also persist and reload its contents as XML and its schema as XML Schema definition language (XSD) schema.
The DataAdapter serves as a bridge between a DataSet and a data source for retrieving and saving data. The DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet to match the data in the data source, and Update, which changes the data in the data source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server database, you can increase overall performance by using the SqlDataAdapter along with its associated SqlCommand and SqlConnection. For other OLE DB-supported databases, use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.
What are the different namespaces used in the project to connect the database? What data providers available in .net to connect to database ?
A: • System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE DB-compatible data sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and read the results.
• System.Data.SqlClient – classes that make up the .NET Framework Data Provider for SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.
• System.Data.Odbc - classes that make up the .NET Framework Data Provider for ODBC. These classes allow you to access ODBC data source in the managed space.
• System.Data.OracleClient - classes that make up the .NET Framework Data Provider for Oracle. These classes allow you to access an Oracle data source in the managed space.
Difference between OLEDB Provider and SqlClient ?
A: SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The SqlClient data provider is fast. It’s faster than the Oracle provider, and faster than accessing database via the OleDb layer. It’s faster because it accesses the native library (which automatically gives you better performance), and it was written with lots of help from the SQL Server team.
What are relation objects in dataset and how & where to use them ?
A: In a DataSet that contains multiple DataTable objects, you can use DataRelation objects to relate one table to another, to navigate through the tables, and to return child or parent rows from a related table. Adding a DataRelation to a DataSet adds, by default, a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.
The following code example creates a DataRelation using two DataTable objects in a DataSet. Each DataTable contains a column named CustID, which serves as a link between the two DataTable objects. The example adds a single DataRelation to the Relations collection of the DataSet. The first argument in the example specifies the name of the DataRelation being created. The second argument sets the parent DataColumn and the third argument sets the child DataColumn.
custDS.Relations.Add(”CustOrders”,
custDS.Tables[”Customers”].Columns[”CustID”],
custDS.Tables[”Orders”].Columns[”CustID”]);
OR
private void CreateRelation()
{
// Get the DataColumn objects from two DataTable objects in a DataSet.
DataColumn parentCol;
DataColumn childCol;
// Code to get the DataSet not shown here.
parentCol = DataSet1.Tables[”Customers”].Columns[”CustID”];
childCol = DataSet1.Tables[”Orders”].Columns[”CustID”];
// Create DataRelation.
DataRelation relCustOrder;
relCustOrder = new DataRelation(”CustomersOrders”, parentCol, childCol);
// Add the relation to the DataSet.
DataSet1.Relations.Add(relCustOrder);
}
How would u connect to database using .NET ?
A: SqlConnection nwindConn = new SqlConnection(”Data Source=localhost; Integrated Security=SSPI;” +
“Initial Catalog=northwind”);
nwindConn.Open();
Advantage of ADO.Net ?
A: o ADO.NET Does Not Depend On Continuously Live Connections
o Database Interactions Are Performed Using Data Commands
o Data Can Be Cached in Datasets
o Datasets Are Independent of Data Sources
o Data Is Persisted as XML
o Schemas Define Data Structures
What is the different between ASP.NET and VB.NET?
A: ASP.Net is an “environment”, and VB.Net is a programming language. You can write ASP.Net pages (called “Web Forms” by Microsoft) using VB.Net (or C#, or J# or Managed C++ or any one of a number of .Net compatible languages).
Confusingly, there is an IDE that Microsoft markets called VB.Net, which allows you to write and compile programs (WinForms, WebForms, class libraries etc) written in the language VB.Net
ASP.Net is simple a library that makes it easy for you to create web applications that run against the .NET runtime (similar to the java runtime).
VB.Net is a language that compiles against the common language runtime, like C#. Any .NET compliant language can use the asp.net libraries to create web applications.
Note : Actually there is not an IDE called VB.Net. Microsoft’s IDE is called Visual Studio.Net which can be used to manage VB.Net, C#, Eiffle, Fortran, and other languages.
How can we create custom controls in ASP.NET?
A: Custom Controls can be created in either of the following 3 methods.
1. Creating as a composite control : This method uses and combines the existing controls to give a custom functionality which can be used across different projects by adding to the control library. This can provide for event bubbling from child controls to the Parent container, custom event handling and properties. The CreateChildControls function of the Control class should be overridden for creating this custom control. This can also support design time rendering of the control.
2. Deriving from an existing control : This method of creating a custom control derives from an existing ASP .Net control and customizing the properties that we need. This also can support custom event handling, properties etc.,
3. Creating a control from Scratch : This method is the one which needs maximum programming. This method needs even the HTML code for the custom controls to be written by the programmer. This may also need one to implement the IPostBackDataHandler and IPostBackEventHandler interfaces. A detailed explanation with example for this is available at Rendering Custom Controls Sample in MSDN.
How many types of validation controls are provided by ASP.NET ?
A; RequiredField Validator Control,Range Validator Control, RegularExpression Validator Control,Custom Validator Control and Validation Summary Control are provided by ASP.NET.
Can you explain what is “AutoPostBack” feature in ASP.NET ?
A: AutoPostBack is built into the form-based server controls, and when enabled, automatically posts the page back to the server whenever the value of the control in question is changed.
How can you enable automatic paging in DataGrid ?
A: Using the Built-In Paging Controls
To use default paging, you set properties to enable paging, set the page size, and specify the style of the paging controls. Paging controls are LinkButton controls. You can choose from these types: Next and previous buttons. The button captions can be any text you want. Page numbers, which allow users to jump to a specific page. You can specify how many numbers are displayed; if there are more pages, an ellipsis ( … ) is displayed next to the numbers. You must also create an event-handling method that responds when users click a navigation control.
To use the built-in paging controlsSet the control’s AllowPaging property to true. Set the PageSize property to the number of items to display per page.
To set the appearance of the paging buttons, include a element into the page as a child of the DataGrid control. For syntax, see DataGrid Control Syntax. Create a handler for the grid’s PageIndexChanged event to respond to a paging request. The DataGridPageChangedEventsArgs enumeration contains the NewPageIndex property, which is the page the user would like to browse to. Set the grid’s CurrentPageIndex property to e.NewPageIndex, then rebind the data.
What is the difference between login controls and Forms authentication?
A: Login controls are an easy way to implement Forms authentication without having to write any code. For example, the Login control performs the same functions you would normally perform when using the FormsAuthentication class—prompt for user credentials, validate them, and issue the authentication ticket—but with all the functionality wrapped in a control that you can just drag from the Toolbox in Visual Studio. Under the covers, the login control uses the FormsAuthentication class (for example, to issue the authentication ticket) and ASP.NET membership (to validate the user credentials). Naturally, you can still use Forms authentication yourself, and applications you have that currently use it will continue to run.
What is Tracing in ASP.NET ?
A: ASP.NET introduces new functionality that allows you to write debug statements, directly in your code, without having to remove them from your application when it is deployed to production servers. Called tracing, this feature allows you to write variables or structures in a page, assert whether a condition is met, or simply trace through the execution path of your page or application.
How do we enable tracing ?
A; Instead of enabling tracing for individual pages, you can enable it for your entire application. In that case, every page in your application displays trace information. Application tracing is useful when you are developing an application because you can easily enable it and disable it without editing individual pages. When your application is complete, you can turn off tracing for all pages at once.When you enable tracing for an application, ASP.NET collects trace information for each request to the application, up to the maximum number of requests you specify. The default number of requests is 10. You can view trace information with the trace viewer.By default, when the trace viewer reaches its request limit, the application stops storing trace requests. However, you can configure application-level tracing to always store the most recent tracing data, discarding the oldest data when the maximum number of requests is reached.
To Enable Tracing for an application:
1.Open your Web site’s Web.config file. If no Web.config file exists, create a new file in the root folder and copy the following into it:
2.Add a trace element as a child of the system.web element.
3.In the trace element, set the enabled attribute to true.
4.If you want trace information to appear at the end of the page that it is associated with, set the trace element’s pageOutput attribute to true. If you want tracing information to be displayed only in the trace viewer, set the pageOutput attribute to false.For example, the following application trace configuration collects trace information for up to 40 requests and allows browsers on computers other than the server of origin to display the trace viewer. Trace information is not displayed in individual pages.
What exactly happens when ASPX page is requested from Browser?
A: At its core, the ASP.NET execution engine compiles the page into a class, which derives from the code behind class (which in turn derives directly or indirectly from the Page class). Then it injects the newly created class into the execution environment, instantiates it, and executes it. ASP.NET, on the other hand, can accept code in any language that is compatible with the .NET framework, because it’s compiled down natively just like other code.
How do you deploy an ASP.NET application?
You can deploy an ASP.NET Web application using any one of the following three deployment options.1.XCOPY Deployment
2.Using the Copy Project option in VS .NET
3.Deployment using VS.NET installer
ASP.NET Configuration.
A: ASP.NET Configuration
The ASP.NET configuration system features an extensible infrastructure that enables you to define configuration settings at the time your ASP.NET applications are first deployed so that you can add or revise configuration settings at any time with minimal impact on operational Web applications and servers.
The ASP.NET configuration system provides the following benefits:
* Configuration information is stored in XML-based text files. You can use any standard text editor or XML parser to create and edit ASP.NET configuration files.
* Multiple configuration files, all named Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies configuration settings to its own directory and all child directories below it. Configuration files in child directories can supply configuration information in addition to that inherited from parent directories, and the child directory configuration settings can override or modify settings defined in parent directories. The root configuration file named systemroot\Microsoft.NET\Framework\versionNumber\CONFIG\Machine.config provides ASP.NET configuration settings for the entire Web server.
* At run time, ASP.NET uses the configuration information provided by the Web.config files in a hierarchical virtual directory structure to compute a collection of configuration settings for each unique URL resource. The resulting configuration settings are then cached for all subsequent requests to a resource. Note that inheritance is defined by the incoming request path (the URL), not the file system paths to the resources on disk (the physical paths).
* ASP.NET detects changes to configuration files and automatically applies new configuration settings to Web resources affected by the changes. The server does not have to be rebooted for the changes to take effect. Hierarchical configuration settings are automatically recalculated and recached whenever a configuration file in the hierarchy is changed. The
section is an exception.
* The ASP.NET configuration system is extensible. You can define new configuration parameters and write configuration section handlers to process them.
* ASP.NET help protect configuration files from outside access by configuring Internet Information Services (IIS) to prevent direct browser access to configuration files. HTTP access error 403 (forbidden) is returned to any browser attempting to request a configuration file directly.
What can be stored in Web.config file?
A: There are number of important settings that can be stored in the configuration file. Here are some of the most frequently used configurations, stored conveniently inside Web.config file..
1. Database connections
2. Session States
3. Error Handling
4. Security
Difference between Web.config and machine.config?
A: web.config:
Web.config file, as it sounds like is a configuration file for the Asp .net web application. An Asp .net application has one web.config file which keeps the configurations required for the corresponding application. Web.config file is written in XML with specific tags having specific meanings.
machine.config
As web.config file is used to configure one asp .net web application, same way Machine.config file is used to configure the application according to a particular machine. That is, configuration done in machine.config file is affected on any application that runs on a particular machine. Usually, this file is not altered and only web.config is used which configuring applications
Where we can use DLL made in C#.Net ?
A: Supporting .Net, bcoz DLL made in C#.Net semicompiled version. Its not a com object. It is used only in .Net Framework.As it is to be compiled at runtime to byte code.
If A.equals(B) is true then A.getHashcode & B.getHashCode must always return same hash code.
A: The answer is False because it is given that A.equals(B) returns true i.e. objects are equal and now its hashCode is asked which is always independent of the fact that whether objects are equal or not. So, GetHashCode for both of the objects returns different value.
To Configure .Net for JIT activation what do you do?
A: Actually JIT activation is required for COM+ components which can be done by setting JustInTimeActivation attribute to true (choice A). For .net applications / components JIT comes in by default.
How do you import Activex component in to .NET?
A: An application called AXImp.exe shipped with .Net SDK is used.
This application does something similar as Tlbimp.exe does for non graphical COM components.
It creates a wrapper component that contains the type information that the .Net runtime can understand.
What is the use of fixed statement?
A: The fixed statement sets a pointer to a managed variable and “pins” that variable during the execution of statement.
Without fixed, pointers to managed variables would be of little use since garbage collection could relocate the variables unpredictably. (In fact, the C# compiler will not allow you to set a pointer to a managed variable except in a fixed statement.)
Eg:
Class A { public int i; }
A objA = new A; // A is a .net managed type
fixed(int *pt = &objA.i) // use fixed while using pointers with managed
// variables
{
*pt=45; // in this block use the pointer the way u want
}
What is the order of destructors called in a polymorphism hierarchy?
A: Destructors are called in reverse order of constructors. First destructor of most derived class is called followed by its parent’s destructor and so on till the topmost class in the hierarchy.
You don’t have control over when the first destructor will be called, since it is determined by the garbage collector. Sometime after the object goes out of scope GC calls the destructor, then its parent’s destructor and so on.
When a program terminates definitely all object’s destructors are called.
How can you sort the elements of the array in descending order?
A: int[] arr = new int[3];
arr[0] = 4;
arr[1] = 1;
arr[2] = 5;
Array.Sort(arr);
Array.Reverse(arr);
Is it possible to Override Private Virtual methods.
A: No, First of all you cannot declare a method as ‘private virtual’.
What does the volatile modifier do?
A: The system always reads the current value of a volatile object at the point it is requested, even if the previous instruction asked for a value from the same object. Also, the value of the object is written immediately on assignment.
The volatile modifier is usually used for a field that is accessed by multiple threads without using the lock statement to serialize access. Using the volatile modifier ensures that one thread retrieves the most up-to-date value written by another thread.
Is it possible to debug the classes written in other .Net languages in a C# project.?
A: It is definitely possible to debug other .Net languages code in a C# project. As everyone knows .net can combine code written in several .net languages into one single assembly. Same is true with debugging.
How do you debug an ASP.NET Web application?
A: Attach the aspnet_wp.exe process to the DbgClr debugger.
What debugging tools come with the .NET SDK?
A: 1. CorDBG – command-line debugger. To use CorDbg, you must compile the original C# file using the /debug switch.
2. DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR.
What is the difference between structures and enumeration?
A: Unlike classes, structs are value types and do not require heap allocation. A variable of a struct type directly contains the data of the struct, whereas a variable of a class type contains a reference to the data. They are derived from System.ValueType class.
Enum->An enum type is a distinct type that declares a set of named constants.They are strongly typed constants. They are unique types that allow to declare symbolic names to integral values. Enums are value types, which means they contain their own value, can’t inherit or be inherited from and assignment copies the value of one enum to another.
public enum Grade
{
A,
B,
C
}
What is Value type and refernce type in .Net?
A: Value Type : A variable of a value type always contains a value of that type. The assignment to a variable of a value type creates a copy of the assigned value, while the assignment to a variable of a reference type creates a copy of the reference but not of the referenced object.
The value types consist of two main categories:
* Stuct Type
* Enumeration Type
Reference Type :Variables of reference types, referred to as objects, store references to the actual data. This section introduces the following keywords used to declare reference types:
* Class
* Interface
* Delegate
This section also introduces the following built-in reference types:
* object
* string
What are the types of assemblies?
A: Static assemblies
These are the .NET PE files that you create at compile time.
Dynamic assemblies
These are PE-formatted, in-memory assemblies that you dynamically create at runtime using the classes in the System.Reflection.Emit namespace.
Private assemblies
These are static assemblies used by a specific application.
Public or shared assemblies These are static assemblies that must have a unique shared name and can be used by any application.
An application uses a private assembly by referring to the assembly using a static path or through an XML-based application configuration file. While the CLR doesn’t enforce versioning policies-checking whether the correct version is used-for private assemblies, it ensures that an application uses the correct shared assemblies with which the application was built. Thus, an application uses a specific shared assembly by referring to the specific shared assembly, and the CLR ensures that the correct version is loaded at runtime.
In .NET, an assembly is the smallest unit to which you can associate a version number
What is manifest?
A: It is the metadata that describes the assemblies.
What distributed process frameworks outside .NET do you know?
A: Distributed Computing Environment/Remote Procedure Calls (DEC/RPC), Microsoft Distributed Component Object Model (DCOM), Common Object Request Broker Architecture (CORBA), and Java Remote Method Invocation (RMI).
How do you retrieve the customized properties of a .NET application from XML .config file?
A: Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable.
When would you use ErrorProvider control?
A: ErrorProvider control is used in Windows Forms application. It is like Validation Control for ASP.NET pages. ErrorProvider control is used to provide validations in Windows forms and display user friendly messages to the user if the validation fails. E.g. if we went to validate the textBox1 should be empty, then we can validate as below
1). You need to place the errorprovide control on the form
private void textBox1_Validating(object sender,System.ComponentModel.CancelEventArgs e)
{
ValidateName();
}
private bool ValidateName()
{
bool bStatus = true;
if (textBox1.Text == "")
{
errorProvider1.SetError (textBox1,"Please enter your Name");
bStatus = false;
}
else
errorProvider1.SetError (textBox1,"");
return bStatus;
}
it check the textBox1 is empty . If it is empty, then a message Please enter your name is displayed.
What is the difference between Debug.Write and Trace.Write?
A: The Debug.Write call won’t be compiled when the DEBUGsymbol is not defined (when doing a release build). Trace.Write calls will be compiled. Debug.Write is for information you want only in debug builds, Trace.Write is for when you want it in release build as well.
What are different transaction options available for services components?
A: There are 5 transactions types that can be used with COM+. Whenever an object is registered with COM+ it has to abide either to these 5 transaction types.
Disabled: - There is no transaction. COM+ does not provide transaction support for this component.
Not Supported: - Component does not support transactions. Hence even if the calling component in the hierarchy is transaction enabled this component will not participate in the transaction.
Supported: - Components with transaction type supported will be a part of the transaction if the calling component has an active transaction.
If the calling component is not transaction enabled this component will not start a new transaction.
Required: - Components with this attribute require a transaction i.e. either the calling should have a transaction in place else this component will start a new transaction.
Required New: - Components enabled with this transaction type always require a new transaction. Components with required new transaction type instantiate a new transaction for themselves every time.
What does it meant to say “the canonical” form of XML?
A: The purpose of Canonical XML is to define a standard format for an XML document. Canonical XML is a very strict XML syntax, which lets documents in canonical XML be compared directly.
Using this strict syntax makes it easier to see whether two XML documents are the same. For example, a section of text in one document might read Black & White, whereas the same section of text might read Black & White in another document, and even in another. If you compare those three documents byte by byte, they’ll be different. But if you write them all in canonical XML, which specifies every aspect of the syntax you can use, these three documents would all have the same version of this text (which would be Black & White) and could be compared without problem. This Comparison is especially critical when xml documents are digitally signed. The digital signal may be interpreted in different way and the document may be rejected.
What are the mobile devices supported by .net platform?
A: The Microsoft .NET Compact Framework is designed to run on mobile devices such as mobile phones, Personal Digital Assistants (PDAs), and embedded devices. The easiest way to develop and test a Smart Device Application is to use an emulator.
These devices are divided into two main divisions:
1) Those that are directly supported by .NET (Pocket PCs, i-Mode phones, and WAP devices)
2) Those that are not (Palm OS and J2ME-powered devices).
What is a Windows Service and how does its lifecycle differ from a “standard” EXE?
A: Windows service is a application that runs in the background. It is equivalent to a NT service.
The executable created is not a Windows application, and hence you can’t just click and run it . it needs to be installed as a service, VB.Net has a facility where we can add an installer to our program and then use a utility to install the service. Where as this is not the case with standard exe
What is the difference between repeater over datalist and datagrid?
A: The Repeater class is not derived from the WebControl class, like the DataGrid and DataList. Therefore, the Repeater lacks the stylistic properties common to both the DataGrid and DataList. What this boils down to is that if you want to format the data displayed in the Repeater, you must do so in the HTML markup. The Repeater control provides the maximum amount of flexibility over the HTML produced. Whereas the DataGrid wraps the DataSource contents in an HTML < table >, and the DataList wraps the contents in either an HTML < table > or < span > tags (depending on the DataList’s RepeatLayout property), the Repeater adds absolutely no HTML content other than what you explicitly specify in the templates. While using Repeater control, If we wanted to display the employee names in a bold font we’d have to alter the “ItemTemplate” to include an HTML bold tag, Whereas with the DataGrid or DataList, we could have made the text appear in a bold font by setting the control’s ItemStyle-Font-Bold property to True. The Repeater’s lack of stylistic properties can drastically add to the development time metric. For example, imagine that you decide to use the Repeater to display data that needs to be bold, centered, and displayed in a particular font-face with a particular background color. While all this can be specified using a few HTML tags, these tags will quickly clutter the Repeater’s templates. Such clutter makes it much harder to change the look at a later date. Along with its increased development time, the Repeater also lacks any built-in functionality to assist in supporting paging, editing, or editing of data. Due to this lack of feature-support, the Repeater scores poorly on the usability scale.
However, The Repeater’s performance is slightly better than that of the DataList’s, and is more noticeably better than that of the DataGrid’s. Following figure shows the number of requests per second the Repeater could handle versus the DataGrid and DataList
What is a PostBack?
A: The process in which a Web page sends data back to the same page on the server.
Is it possible to prevent a browser from caching an ASPX page?
A: Just call SetNoStore on the HttpCachePolicy object exposed through the Response object’s Cache property, as demonstrated here:
SetNoStore works by returning a Cache-Control: private, no-store header in the HTTP response. In this example, it prevents caching of a Web page that shows the current time.
What are VSDISCO files?
A: VSDISCO files are DISCO files that support dynamic discovery of Web services. If you place the following VSDISCO file in a directory on your Web server, for example, it returns references to all ASMX and DISCO files in the host directory and any subdirectories not noted in elements:
Name two properties common in every validation control?
A: ControlToValidate property and Text property.
What namespace does the Web page belong in the .NET Framework class hierarchy?
A: System.Web.UI.Page
Are the actual permissions for the application defined at run-time or compile-time?
A: The CLR computes actual permissions at runtime based on code group membership and the calling chain of the code.
What is the difference between authentication and authorization?
A: Authentication happens first. You verify user’s identity based on credentials. Authorization is making sure the user only gets access to the resources he has credentials for.
What is a code group?
A: A code group is a set of assemblies that share a security context.
How can C# app request minimum permissions?
A: Using System.Security.Permissions;
[assembly:FileDialogPermissionAttribute(SecurityAction.RequestMinimum, Unrestricted=true)].
How can you work with permissions from your .NET application?
A: You can request permission to do something and you can demand certain permissions from other apps. You can also refuse permissions so that your app is not inadvertently used to destroy some data.
What’s the difference between code-based security and role-based security? Which one is better?
A: Code security is the approach of using permissions and permission sets for a given code to run. The admin, for example, can disable running executables off the Internet or restrict access to corporate database to only few applications. Role-based security most of the time involves the code running with the privileges of the current user. This way the code cannot supposedly do more harm than mess up a single user account. There’s no better, or 100% thumbs-up approach, depending on the nature of deployment, both code-based and role-based security could be implemented to an extent.
How do you display an editable drop-down list?
A: Displaying a drop-down list requires a template column in the grid. Typically, the ItemTemplate contains a control such as a data-bound Label control to show the current value of a field in the record. You then add a drop-down list to the EditItemTemplate. In Visual Studio, you can add a template column in the Property builder for the grid, and then use standard template editing to remove the default TextBox control from the EditItemTemplate and drag a DropDownList control into it instead. Alternatively, you can add the template column in HTML view. After you have created the template column with the drop-down list in it, there are two tasks. The first is to populate the list. The second is to preselect the appropriate item in the list — for example, if a book’s genre is set to “fiction,” when the drop-down list displays, you often want “fiction” to be preselected.
How to manage pagination in a page?
A: Using pagination option in DataGrid control. We have to set the number of records for a page, then it takes care of pagination by itself.
Can the validation be done in the server side?
A: Client side validation is done by default. Server side validation is also possible. We can switch off the client side and server side can be done.
How do you validate the controls in an ASP .NET page?
A: We can Validate the controls in an ASP.NET page by using special validation controls that are meant for this. We have Range Validator, Email Validator.
What is smart navigation?
A: The cursor position is maintained when the page gets refreshed due to the server side validation and the page gets refreshed.
How is .NET able to support multiple languages?
A: A language should comply with the Common Language Runtime standard to become a .NET language. In .NET, code is compiled to Microsoft Intermediate Language (MSIL for short). This is called as Managed Code. This Managed code is run in .NET environment. So after compilation to this IL the language is not a barrier. A code can call or use a function written in another language.
What is the difference between Java and .NET garbage collectors?
A: Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you’re using. Microsoft standardized on their garbage collection.
What is the CLI? Is it the same as the CLR?
A: The CLI (Common Language Infrastructure) is the definiton of the fundamentals of the .NET framework - the Common Type System (CTS), metadata, the Virtual Execution Environment (VES) and its use of intermediate language (IL), and the support of multiple programming languages via the Common Language Specification (CLS). The CLI is documented through ECMA
The CLR (Common Language Runtime) is Microsoft’s primary implementation of the CLI. Microsoft also have a shared source implementation known as ROTOR, for educational purposes, as well as the .NET Compact Framework for mobile devices. Non-Microsoft CLI implementations include Mono and DotGNU Portable.NET.
What is an application domain?
A: An AppDomain can be thought of as a lightweight process. Multiple AppDomains can exist inside a Win32 process. The primary purpose of the AppDomain is to isolate applications from each other, and so it is particularly useful in hosting scenarios such as ASP.NET. An AppDomain can be destroyed by the host without affecting other AppDomains in the process.
Win32 processes provide isolation by having distinct memory address spaces. This is effective, but expensive. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other’s memory.
One non-obvious use of AppDomains is for unloading types. Currently the only way to unload a .NET type is to destroy the AppDomain it is loaded into. This is particularly useful if you create and destroy types on-the-fly via reflection
Does .NET support one-way Web service operations? Does Microsoft SOAP Toolkit support one-way Web service operations?
A: Yes, .NET framework does support one-way messages. To set a void method as one-way operation, set the OneWay property to true on SoapDocumentMethodAttribute or on SoapRpcMethodAttribute attribute. In such cases, the Web service client is intending to just send some notification to the server and not expect any response. The server in such cases returns 202 Accepted HTTP response to the client. And there will be no output message in the WSDL file for such methods. The support for one-way Web service operations was also added in the latest SOAP Toolkit 3.0 release.
Does .NET support validating XML documents against DTDs?
A: Yes, in addition to XDR and XSD schema validation, .NET continues to support the DTD to validate the XML documents. The System.Xml namespace contains a class named XmlValidatingReader that can be used to validate the XML documents.
What is an .ASP file?
A: It is a Text File that contains the combination of the following:
• Text
• HTML tags
• Script Commands
Where would you use an iHTTPModule, and what are the limitations of anyapproach you might take in implementing one?
A: One of ASP.NET’s most useful features is the extensibility of the HTTP pipeline, the path that data takes between client and server. You can use them to extend your ASP.NET applications by adding pre- and post-processing to each HTTP request coming into your application. For example, if you wanted custom authentication facilities for your application, the best technique would be to intercept the request when it comes in and process the request in a custom HTTP module.
Can you configure a .NET Remoting object via XML file?
A: Yes, via machine.config and application level .config file (or web.config in ASP.NET). Application-level XML settings take precedence over machine.config.
How do I change the permission set for a code group?
A: Use caspol. If you are the machine administrator, you can operate at the ‘machine’ level - which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive.
For example, to allow intranet code to do what it likes you might do this: caspol -cg 1.2 FullTrust
Note that because this is more permissive than the default policy (on a standard system), you should only do this at the machine level - doing it at the user level will have no effect.
How to set the debug mode?
A: Debug Mode for ASP.NET applications - To set ASP.NET appplication in debugging mode, edit the application’s web.config and assign the “debug” attribute in < compilation > section to “true” as show below:
< configuration >
< system.web >
< compilation defaultLanguage="vb" debug="true" / >
….
…
..
< / configuration >
This case-sensitive attribute ‘debug tells ASP.NET to generate symbols for dynamically generated files and enables the
debugger to attach to the ASP.NET application. ASP.NET will detect this change automatically, without the need to restart the server. Debug Mode for ASP.NET Webservices - Debugging an XML Web service created with ASP.NET is similar to the debugging an ASP.NET Web application.
What platforms does the .NET Framework run on?
A: The runtime supports Windows XP, Windows 2000, NT4 SP6a and Windows ME/98. Windows 95 is not supported. Some parts of the framework do not work on all platforms - for example, ASP.NET is only supported on Windows XP and Windows 2000. Windows 98/ME cannot be used for development. IIS is not supported on Windows XP Home Edition, and so cannot be used to host ASP.NET. However, the ASP.NET Web Matrix web server does run on XP Home. The Mono project is attempting to implement the .NET framework on Linux.
How do you handle data concurrency in .NET ?
A: One of the key features of the ADO.NET DataSet is that it can be a self-contained and disconnected data store. It can contain the schema and data from several rowsets in DataTable objects as well as information about how to relate the DataTable objects-all in memory. The DataSet neither knows nor cares where the data came from, nor does it need a link to an underlying data source. Because it is data source agnostic you can pass the DataSet around networks or even serialize it to XML and pass it across the Internet without losing any of its features. However, in a disconnected model, concurrency obviously becomes a much bigger problem than it is in a connected model.
In this column, I’ll explore how ADO.NET is equipped to detect and handle concurrency violations. I’ll begin by discussing scenarios in which concurrency violations can occur using the ADO.NET disconnected model. Then I will walk through an ASP.NET application that handles concurrency violations by giving the user the choice to overwrite the changes or to refresh the out-of-sync data and begin editing again. Because part of managing an optimistic concurrency model can involve keeping a timestamp (rowversion) or another type of flag that indicates when a row was last updated, I will show how to implement this type of flag and how to maintain its value after each database update.
What is WSDL?
A: WSDL is the Web Service Description Language, and it is implemented as a specific XML vocabulary. While it’s very much more complex than what can be described here, there are two important aspects to WSDL with which you should be aware. First, WSDL provides instructions to consumers of Web Services to describe the layout and contents of the SOAP packets the Web Service intends to issue. It’s an interface description document, of sorts. And second, it isn’t intended that you read and interpret the WSDL. Rather, WSDL should be processed by machine, typically to generate proxy source code (.NET) or create dynamic proxies on the fly (the SOAP Toolkit or Web Service Behavior).
What does AspCompat=”true” mean and when should I use it?
A: AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects–that is, COM objects registered ThreadingModel=Apartment. That includes all COM objects written with Visual Basic 6.0. AspCompat should also be set to true (regardless of threading model) if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true:
Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available to the COM components by placing unmanaged wrappers around the equivalent ASP.NET objects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the request for the page) and the COM objects it creates share an apartment. AspCompat=”true” forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel=Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat=”true,” request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it’s marshaled across apartment boundaries.
Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don’t access ASP intrinsic objects and that are registered ThreadingModel=Free or ThreadingModel=Both.
What is Web Gardening? How would using it affect a design?
A: The Web Garden Model: The Web garden model is configurable through the section of the machine.config file. Notice that the section is the only configuration section that cannot be placed in an application-specific web.config file. This means that the Web garden mode applies to all applications running on the machine. However, by using the node in the machine.config source, you can adapt machine-wide settings on a per-application basis.
Two attributes in the section affect the Web garden model. They are webGarden and cpuMask. The webGarden attribute takes a Boolean value that indicates whether or not multiple worker processes (one per each affinitized CPU) have to be used. The attribute is set to false by default. The cpuMask attribute stores a DWORD value whose binary representation provides a bit mask for the CPUs that are eligible to run the ASP.NET worker process. The default value is -1 (0xFFFFFF), which means that all available CPUs can be used. The contents of the cpuMask attribute is ignored when the webGarden attribute is false. The cpuMask attribute also sets an upper bound to the number of copies of aspnet_wp.exe that are running.
Web gardening enables multiple worker processes to run at the same time. However, you should note that all processes will have their own copy of application state, in-process session state, ASP.NET cache, static data, and all that is needed to run applications. When the Web garden mode is enabled, the ASP.NET ISAPI launches as many worker processes as there are CPUs, each a full clone of the next (and each affinitized with the corresponding CPU). To balance the workload, incoming requests are partitioned among running processes in a round-robin manner. Worker processes get recycled as in the single processor case. Note that ASP.NET inherits any CPU usage restriction from the operating system and doesn’t include any custom semantics for doing this.
All in all, the Web garden model is not necessarily a big win for all applications. The more stateful applications are, the more they risk to pay in terms of real performance. Working data is stored in blocks of shared memory so that any changes entered by a process are immediately visible to others. However, for the time it takes to service a request, working data is copied in the context of the process. Each worker process, therefore, will handle its own copy of working data, and the more stateful the application, the higher the cost in performance. In this context, careful and savvy application benchmarking is an absolute must.
Changes made to the section of the configuration file are effective only after IIS is restarted. In IIS 6, Web gardening parameters are stored in the IIS metabase; the webGarden and cpuMask attributes are ignored.
Can we handle the error and redirect to some pages using web.config?
A: Yes, we can do this, but to handle errors, we must know the error codes; only then we can take the user to a proper error message page, else it may confuse the user.
CustomErrors Configuration section in web.config file:
The default configuration is:
< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" >
< error statusCode="404" redirect="Notfound.aspx" / >
< /customErrors >
If mode is set to Off, custom error messages will be disabled. Users will receive detailed exception error messages.
If mode is set to On, custom error messages will be enabled.
If mode is set to RemoteOnly, then users will receive custom errors, but users accessing the site locally will receive detailed error messages.
Add an < error > tag for each error you want to handle. The error tag will redirect the user to the Notfound.aspx page when the site returns the 404 (Page not found) error.
[Example]
There is a page MainForm.aspx
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
‘Put user code to initialize the page here
Dim str As System.Text.StringBuilder
str.Append(”hi”) ‘ Error Line as str is not instantiated
Response.Write(str.ToString)
End Sub
[Web.Config]
< customErrors mode="On" defaultRedirect="Error.aspx"/ >
‘ a simple redirect will take the user to Error.aspx [user defined] error file.
< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" >
< error statusCode="404" redirect="Notfound.aspx" / >
< /customErrors >
‘This will take the user to NotFound.aspx defined in IIS.
What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?
A: ViewState is the mechanism ASP.NET uses to keep track of server control state values that don’t otherwise post back as part of the HTTP form. ViewState Maintains the UI State of a Page
ViewState is base64-encoded. It is not encrypted but it can be encrypted by setting EnableViewStatMAC=”true” & setting the machineKey validation type to 3DES. If you want to NOT maintain the ViewState, include the directive < %@ Page EnableViewState="false" % > at the top of an .aspx page or add the attribute EnableViewState=”false” to any control.
When you’re running a component within ASP.NET, what process is it running within on Windows XP? Windows 2000? Windows 2003?
A: On Windows 2003 (IIS 6.0) running in native mode, the component is running within the w3wp.exe process associated with the application pool which has been configured for the web application containing the component.
On Windows 2003 in IIS 5.0 emulation mode, 2000, or XP, it’s running within the IIS helper process whose name I do not remember, it being quite a while since I last used IIS 5.0.
Difference between asp and asp.net?.
A: “ASP (Active Server Pages) and ASP.NET are both server side technologies for building web sites and web applications, ASP.NET is Managed compiled code - asp is interpreted. and ASP.net is fully Object oriented. ASP.NET has been entirely re-architected to provide a highly productive programming experience based on the .NET Framework, and a robust infrastructure for building reliable and scalable web
applications.”
What is advantage of viewstate and what are benefits?
A: When a form is submitted in classic ASP, all form values are cleared. Suppose you have submitted a form with a lot of information and the server comes back with an error. You will have to go back to the form and correct the information. You click the back button, and what happens…….ALL form values are CLEARED, and you will have to start all over again! The site did not maintain your ViewState.With ASP .NET, the form reappears in the browser window together with all form values.This is because ASP .NET maintains your ViewState. The ViewState indicates the status of the page when submitted to the server.
What is an HTML “entity”?
A: An entity is a specific character string that has the effect of causing a formatting program to select and present a particular character or notation.
Difference between Anchor and Dock Properties?
A: Dock Property->Gets or sets which edge of the parent container a control is docked to. A control can be docked to one edge of its parent container or can be docked to all edges and fill the parent container. For example, if you set this property to DockStyle.Left, the left edge of thecontrol will be docked to the left edge of its parent control. Additionally, the docked edge of the control is resized to match that of its container
control.
Anchor Property->Gets or sets which edges of the control are anchored to the edges of its container. A control can be anchored to one or more edges of its parent container. Anchoring a control to its parent ensures that the anchored edges remain in the same position relative to the edges of the parent container when the parent container is resized.
What’s the safest way to deploy a Windows Forms app?
A: Web deployment: the user always downloads the latest version of the code, the program runs within security sandbox, properly written app will not require additional security privileges.
What class does Icon derive from?
A: Isn’t it just a Bitmap with a wrapper name around it? No, Icon lives in System.Drawing namespace. It’s not a Bitmap by default, and is treated separately by .NET. However, you can use ToBitmap method to get a valid Bitmap object from a valid Icon object.
When displaying fonts, what’s the difference between pixels, points and ems?
A: A pixel is the lowest-resolution dot the computer monitor supports. Its size depends on user’s settings and monitor size. A point is always 1/72 of an inch. An em is the number of pixels that it takes to display the letter M.
Where on the Internet would you look for Web services?
A: UDDI repositaries like uddi.microsoft.com, IBM UDDI node, UDDI Registries in Google Directory, enthusiast sites like XMethods.net.
What is the transport protocol you use to call a Web service?
A: SOAP. Transport Protocols: It is essential for the acceptance of Web Services that they are based on established Internet infrastructure. This in fact imposes the usage of of the HTTP, SMTP and FTP protocols based on the TCP/IP family of transports. Messaging Protocol: The format of messages exchanged between Web Services clients and Web Services should be vendor neutral and should not carry details about the technology used to implement the service. Also, the message format should allow for extensions and different bindings to specific transport protocols. SOAP and ebXML Transport are specifications which fulfill these requirements. We expect that the W3C XML Protocol Working Group defines a successor standard.
How do you turn off cookies for one page in your site?
A: Use the Cookie.Discard Property which Gets or sets the discard flag set by the server. When true, thisproperty instructs the client application not to save the Cookie on the user’s hard disk when a session ends.
Whats an assembly?
A: Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly.
What are CAO’s i.e. Client Activated Objects ?
A: Client-activated objects are objects whose lifetimes are controlled by the calling application domain, just as they would be if the object were local to the client. With client activation, a round trip to the server occurs when the client tries to create an instance of the server object, and the client proxy is created using an object reference (ObjRef) obtained on return from the creation of the remote object on the server. Each time a client creates an instance of a client-activated type, that instance will service only that particular reference in that particular client until its lease expires and its memory is recycled. If a calling application domain creates two new instances of the remote type, each of the client references will invoke only the particular instance in the server application domain from which the reference was returned.
In COM, clients hold an object in memory by holding a reference to it. When the last client releases its last reference, the object can delete itself. Client activation provides the same client control over the server object’s lifetime, but without the complexity of maintaining references or the constant pinging to confirm the continued existence of the server or client. Instead, client-activated objects use lifetime leases to determine how long they should continue to exist. When a client creates a remote object, it can specify a default length of time that the object should exist. If the remote object reaches its default lifetime limit, it contacts the client to ask whether it should continue to exist, and if so, for how much longer. If the client is not currently available, a default time is also specified for how long the server object should wait while trying to contact the client before marking itself for garbage collection. The client might even request an indefinite default lifetime, effectively preventing the remote object from ever being recycled until the server application domain is torn down. The difference between this and a server-activated indefinite lifetime is that an indefinite server-activated object will serve all client requests for that type, whereas the client-activated instances serve only the client and the reference that was responsible for their creation. For more information, see Lifetime Leases.
To create an instance of a client-activated type, clients either configure their application programmatically (or using a configuration file) and call new (New in Visual Basic), or they pass the remote object’s configuration in a call to Activator.CreateInstance. The following code example shows such a call, assuming a TcpChannel has been registered to listen on port 8080.
What is Com Callable wrapper?when it will created?
A: .NET components are accessed from COM via a COM Callable Wrapper (CCW). This is similar to a RCW, but works in the opposite direction. Again, if the wrapper cannot be automatically generated by the .NET development tools, or if the automatic behaviour is not desirable, a custom CCW can be developed. Also, for COM to ’see’ the .NET component, the .NET component must be registered in the registry.CCWs also manage the object identity and object lifetime of the managed objects they wrap.
What is Runtime Callable wrapper?.when it will created?.
A: The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW). Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a .NET client and a COM object. This wrapper turns the COM interfaces exposed by the COM component into .NET-compatible interfaces. For oleautomation (attribute indicates that an interface is compatible with Automation) interfaces, the RCW can be generated automatically from a type library. For non-oleautomation interfaces, it may be necessary to develop a custom RCW which manually maps the types exposed by the COM interface to .NET-compatible types.
What’s the difference between WindowsDefaultLocation and WindowsDefaultBounds?
A: WindowsDefaultLocation tells the form to start up at a location selected by OS, but with internally specified size. WindowsDefaultBounds delegates both size and starting position choices to the OS.
What’s the safest way to deploy a Windows Forms app?
A: Web deployment: the user always downloads the latest version of the code, the program runs within security sandbox, properly written app will not require additional security privileges.
What’s a proxy of the server object in .NET Remoting?
A; It’s a fake copy of the server object that resides on the client side and behaves as if it was the server. It handles the communication between real server object and the client object. This process is also known as marshaling.
When would you use .NET Remoting and when Web services?
A: Use remoting for more efficient exchange of information when you control both ends of the application. Use Web services for open-protocol-based information exchange when you are just a client or a server with the other end belonging to someone else.
What are channels in .NET Remoting?
A: Channels represent the objects that transfer the other serialized objects from one application domain to another and from one computer to another, as well as one process to another on the same box. A channel must exist before an object can be transferred.
What security measures exist for .NET Remoting in System.Runtime.Remoting?
A: Security should be taken care of at the application level. Cryptography and other security techniques can be applied at application or server level.
What technology enables out-of-proc communication in .NET?
A: Most usually Remoting;.NET remoting enables client applications to use objects in other processes on the same computer or on any other computer available on its network.While you could implement an out-of-proc component in any number of other ways, someone using the term almost always means Remoting.
What is ADO .NET and what is difference between ADO and ADO.NET?
A: ADO.NET is stateless mechanism. I can treat the ADO.Net as a separate in-memory database where in I can use relationships between the tables and select insert and updates to the database. I can update the actual database as a batch.
Can you declare a C++ type destructor in C# like ~MyClass()?
A: Yes, but what’s the point, since it will call Finalize(), and Finalize() has no guarantees when the memory will be cleaned up, plus, it introduces additional load on the garbage collector.
Contrast DTDs versus XSDs. What are their similarities and differences? Which is preferred and why?
A: Document Type Definition (DTD) describes a model or set of rules for an XML document. XML Schema Definition (XSD) also describes the structure of an XML document but XSDs are much more powerful. The disadvantage with the Document Type Definition is it doesn’t support data types beyond the basic 10 primitive types. It cannot properly define the type of data contained by the tag. An Xml Schema provides an Object Oriented approach to defining the format of an xml document. The Xml schema support most basic programming types like integer, byte, string, float etc., We can also define complex types of our own which can be used to define a xml document. Xml Schemas are always preferred over DTDs as a document can be more precisely defined using the XML Schemas because of its rich support for data representation.
Why is the XML InfoSet specification different from the Xml DOM? What does the InfoSet attempt to solve?
A: “The XML Information Set (Infoset) defines a data model for XML. The Infoset describes the abstract representation of an XML Document. Infoset is the generalized representation of the XML Document, which is primarily meant to act as a set of definitions used by XML technologies to formally describe what parts of an XML document they operate upon.
The Document Object Model (DOM) is one technology for representing an XML Document in memory and to programmatically read, modify and manipulate a xml document. Infoset helps defining generalized standards on how to use XML that is not dependent or tied to a particular XML specification or API. The Infoset tells us what part of XML Document should be considered as significant information.
How does VB.NET/C# achieve polymorphism?
A: Polymorphism is also achieved through interfaces. Like abstract classes, interfaces also describe the methods that a class needs to implement. The difference between abstract classes and interfaces is that abstract classes always act as a base class of the related classes in the class hierarchy. For example, consider a hierarchy-car and truck classes derived from four-wheeler class; the classes two-wheeler and four-wheeler derived from an abstract class vehicle. So, the class ‘vehicle’ is the base class in the class hierarchy. On the other hand dissimilar classes can implement one interface. For example, there is an interface that compares two objects. This interface can be implemented by the classes like box, person and string, which are unrelated to each other.
C# allows multiple interface inheritance. It means that a class can implement more than one interface. The methods declared in an interface are implicitly abstract. If a class implements an interface, it becomes mandatory for the class to override all the methods declared in the interface, otherwise the derived class would become abstract.
Can you explain what inheritance is and an example of when you might use it? The savingaccount class has two data members-accno that stores account number, and trans that keeps track of the number of transactions. We can create an object of savingaccount class as shown below.
savingaccount s = new savingaccount ( “Amar”, 5600.00f ) ;
From the constructor of savingaccount class we have called the two-argument constructor of the account class using the base keyword and passed the name and balance to this constructor using which the data member’s name and balance are initialised.
We can write our own definition of a method that already exists in a base class. This is called method overriding. We have overridden the deposit( ) and withdraw( ) methods in the savingaccount class so that we can make sure that each account maintains a minimum balance of Rs. 500 and the total number of transactions do not exceed 10. From these methods we have called the base class’s methods to update the balance using the base keyword. We have also overridden the display( ) method to display additional information, i.e. account number.
Working of currentaccount class is more or less similar to that of savingaccount class. Using the derived class’s object, if we call a method that is not overridden in the derived class, the base class method gets executed. Using derived class’s object we can call base class’s methods, but the reverse is not allowed.
Unlike C++, C# does not support multiple inheritance. So, in C# every class has exactly one base class. Now, suppose we declare reference to the base class and store in it the address of instance of derived class as shown below.
account a1 = new savingaccount ( “Amar”, 5600.00f ) ;
account a2 = new currentaccount ( “MyCompany Pvt. Ltd.”, 126000.00f) ;
Such a situation arises when we have to decide at run-time a method of which class in a class hierarchy should get called. Using a1 and a2, suppose we call the method display( ), ideally the method of derived class should get called. But it is the method of base class that gets called. This is because the compiler considers the type of reference (account in this case) and resolves the method call. So, to call the proper method we must make a small change in our program. We must use the virtual keyword while defining the methods in base class as shown below.
public virtual void display( ) { }
We must declare the methods as virtual if they are going to be overridden in derived class. To override a virtual method in derived classes we must use the override keyword as given below.
public override void display( ) { }
Now it is ensured that when we call the methods using upcasted reference, it is the derived class’s method that would get called. Actually, when we declare a virtual method, while calling it, the compiler considers the contents of the reference rather than its type.
If we don’t want to override base class’s virtual method, we can declare it with new modifier in derived class. The new modifier indicates that the method is new to this class and is not an override of a base class method.
What is Jit compilers?.how many are available in clr?
A: Just-In-Time compiler- it converts the language that you write in .Net into machine language that a computer can understand. there are tqo types of JITs one is memory optimized & other is performace optimized.
What is MSIL?
A: When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Before code can be run, MSIL must be converted to CPU-specific code, usually by a just-in-time (JIT) compiler. Because the common language runtime supplies one or more JIT compilers for each computer architecture it supports, the same set of MSIL can be JIT-compiled and run on any supported architecture.
When a compiler produces MSIL, it also produces metadata. Metadata describes the types in your code, including the definition of each type, the signatures of each type’s members, the members that your code references, and other data that the runtime uses at execution time. The MSIL and metadata are contained in a portable executable (PE) file that is based on and extends the published Microsoft PE and common object file format (COFF) used historically for executable content. This file format, which accommodates MSIL or native code as well as metadata, enables the operating system to recognize common language runtime images. The presence of metadata in the file along with the MSIL enables your code to describe itself, which means that there is no need for type libraries or Interface Definition Language (IDL). The runtime locates and extracts the metadata from the file as needed during execution.
What is global assembly cache?
A: Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer. There are several ways to deploy an assembly into the global assembly cache:
• Use an installer designed to work with the global assembly cache. This is the preferred option for installing assemblies into the global assembly cache. Use a developer tool called the Global Assembly Cache tool (Gacutil.exe), provided by the .NET Framework SDK.
• Use Windows Explorer to drag assemblies into the cache.
What is namespaces?.
A: Namespace is a logical naming scheme for group related types.Some class types that logically belong together they can be put into a common namespace. They prevent namespace collisions and they provide scoping. They are imported as “using” in C# or “Imports” in Visual Basic. It seems as if these directives specify a particular assembly, but they don’t. A namespace can span multiple assemblies, and an assembly can define multiple namespaces. When the compiler needs the definition for a class type, it tracks through each of the different imported namespaces to the type name and searches each referenced assembly until it is found.
Namespaces can be nested. This is very similar to packages in Java as far as scoping is concerned.
What are delegates?where are they used ?
A: A delegate defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure.
What is a formatter?
A; A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing and decoding messages into data on the other end.
Are private class-level variables inherited?
A: Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
Different b/w .NET & J2EE ?
A: Differences between J2EE and the .NET Platform
Vendor Neutrality
The .NET platform is not vendor neutral, it is tied to the Microsoft operating systems. But neither are any of the J2EE implementations
Many companies buy into J2EE believing that it will give them vendor neutrality. And, in fact, this is a stated goal of Sun’s vision:
A wide variety of J2EE product configurations and implementations, all of which meet the requirements of this specification, are possible. A portable J2EE application will function correctly when successfully deployed in any of these products. (ref : Java 2 Platform Enterprise Edition Specification, v1.3, page 2-7 available at http://java.sun.com/j2ee/)
Overall Maturity
Given that the .NET platform has a three year lead over J2EE, it should be no surprise to learn that the .NET platform is far more mature than the J2EE platform. Whereas we have high volume highly reliable web sites using .NET technologies (NASDAQ and Dell being among many examples)
Interoperability and Web Services
The .NET platform eCollaboration model is, as I have discussed at length, based on the UDDI and SOAP standards. These standards are widely supported by more than 100 companies. Microsoft, along with IBM and Ariba, are the leaders in this area. Sun is a member of the UDDI consortium and recognizes the importance of the UDDI standards.
In a recent press release, Sun’s George Paolini, Vice President for the Java Community
Development, says:”Sun has always worked to help establish and support open, standards-based technologies that facilitate the growth of network-based applications, and we see UDDI as an important project to establish a registry framework for business-to-business e-commerce
But while Sun publicly says it believes in the UDDI standards, in reality, Sun has done nothing whatsoever to incorporate any of the UDDI standards into J2EE.
Framework Support
The .NET platform includes such an eCommerce framework called Commerce Server. At this point, there is no equivalent vendor-neutral framework in the J2EE space. With J2EE, you should assume that you will be building your new eCommerce solution from scratch
Moreover, no matter what [J2EE] vendor you choose, if you expect a component framework that will allow you to quickly field complete e-business applications, you are in for a frustrating experience
Language
In the language arena, the choice is about as simple as it gets. J2EE supports Java, and only Java. It will not support any other language in the foreseeable future. The .NET platform supports every language except Java (although it does support a language that is syntactically and functionally equivalent to Java, C#). In fact, given the importance of the .NET platform as a language independent vehicle, it is likely that any language that comes out in the near future will include support for the .NET platform.
Some companies are under the impression that J2EE supports other languages. Although both IBM’s WebSphere and BEA’s WebLogic support other languages, neither does it through their J2EE technology. There are only two official ways in the J2EE platform to access other languages, one through the Java Native Interface and the other through CORBA interoperability. Sun recommends the later approach. As Sun’s Distinguished Scientist and Java Architect Rick Cattell said in a recent interview.
Portability
The reason that operating system portability is a possibility with J2EE is not so much because of any inherent portability of J2EE, as it is that most of the J2EE vendors support multiple operating systems. Therefore as long as one sticks with a given J2EE vendor and a given database vendor, moving from one operating system to another should be possible. This is probably the single most important benefit in favor of J2EE over the .NET platform, which is limited to the Windows operating system. It is worth noting, however, that Microsoft has submitted the specifications for C# and a subset of the .NET Framework (called the common language infrastructure) to ECMA, the group that standardizes JavaScript.
J2EE offers an acceptable solution to ISVs when the product must be marketed to non-Windows customers, particularly when the J2EE platform itself can be bundled with the ISV’s product as an integrated offering.
If the primary customer base for the ISV is Windows customers, then the .NET platform should be chosen. It will provide much better performance at a much lower cost.
Client device independence
The major difference being that with Java, it is the presentation tier programmer that determines the ultimate HTML that will be delivered to the client, and with .NET, it is a Visual Studio.NET control.
This Java approach has three problems. First, it requires a lot of code on the presentation tier, since every possible thin client system requires a different code path. Second, it is very difficult to test the code with every possible thin client system. Third, it is very difficult to add new thin clients to an existing application, since to do so involves searching through, and modifying a tremendous amount of presentation tier logic.
The .NET Framework approach is to write device independent code that interacts with visual controls. It is the control, not the programmer, that is responsible for determining what HTML to deliver, based on the capabilities of the client device.. In the .NET Framework model, one can forget that such a thing as HTML even exists!
Conclusion
Sun’s J2EE vision is based on a family of specifications that can be implemented by many vendors. It is open in the sense that any company can license and implement the technology, but closed in the sense that it is controlled by a single vendor, and a self contained architectural island with very limited ability to interact outside of itself. One of J2EE’s major disadvantages is that the choice of the platform dictates the use of a single programming language, and a programming language that is not well suited for most businesses. One of J2EE’s major advantages is that most of the J2EE vendors do offer operating system portability.
Microsoft’s .NET platform vision is a family of products rather than specifications, with specifications used primarily to define points of interoperability. The major disadvantage of this approach is that if is limited to the Windows platform, so applications written for the .NET platform can only be run on .NET platforms. Their are several important advantages to the .NET platform:
* The cost of developing applications is much lower, since standard business languages can be used and device independent presentation tier logic can be written.
* The cost of running applications is much lower, since commodity hardware platforms (at 1/5 the cost of their Unix counterparts) can be used.
* The ability to scale up is much greater, with the proved ability to support at least ten times the number of clients any J2EE platform has shown itself able to support.
* Interoperability is much stronger, with industry standard eCollaboration built into the platform.
What’s the difference between System.String and System.StringBuilder classes?
A: System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
What’s the difference between an interface and abstract class?
A: In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
And if they have conflicting method names?
A: It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
What are three test cases you should go through in unit testing?
A: Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
What’s the difference between the Debug class and Trace class?
A; Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
How’s the DLL Hell problem solved in .NET?
A: Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
Can multiple catch blocks be executed?
A: It’s a delegate that points to and eventually fires off several methods.
What’s the difference between const and readonly?
A: You can initialize readonly variables to some runtime values. Let’s say your program uses current date and time as one of the values that won’t change. This way you declare public readonly string DateT = new DateTime().ToString().
What’s the difference between Java and .NET garbage collectors?
A: Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you’re using. Microsoft standardized on their garbage collection.
What are the types of authentication in .net?
A: We have three types of authentication:
. Form authenticatio
. Windows authentication
. Passport This has to be declared in web.config file.
What is difference between constants, readonly and, static ?
A: Constants: The value can’t be changed
Read-only: The value will be initialized only once from the constructor of the class.
Static: Value can be initialized once.
What is the difference between a Struct and a Class ?
A: The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is less expensive. When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will remain unassigned and the object cannot be used until all of the fields are initialized. It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always provided to initialize the struct members to their default values.
It is an error to initialize an instance field in a struct.
There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.
A struct is a value type, while a class is a reference type.
What is Reference type and value type ?
A: Reference Type: Reference types are allocated on the managed CLR heap, just like object types. A data type that is stored as a reference to the value’s location. The value of a reference type is the location of the sequence of bits that represent the type’s data. Reference types can be self-describing types, pointer types, or interface types
Value Type: Value types are allocated on the stack just like primitive types in VBScript, VB6 and C/C++. Value types are not instantiated using new go out of scope when the function they are defined within returns.
Value types in the CLR are defined as types that derive from system.valueType.
A data type that fully describes a value by specifying the sequence of bits that constitutes the value’s representation. Type information for a value type instance is not stored with the instance at run time, but it is available in metadata. Value type instances can be treated as objects using boxing.
What is MSIL, IL, CTS and, CLR ?
A: MSIL: (Microsoft intermediate language) When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Before code can be executed, MSIL must be converted to CPU-specific code, usually by a just-in-time (JIT) compiler. Because the common language runtime supplies one or more JIT compilers for each computer architecture it supports, the same set of MSIL can be JIT-compiled and executed on any supported architecture. When a compiler produces MSIL, it also produces metadata. Metadata describes the types in your code, including the definition of
each type, the signatures of each type’s members, the members that our code references, and other data that the runtime uses at execution time. The MSIL and metadata are contained in a portable executable (PE) file that is based on and extends the published Microsoft PE and Common Object File Format (COFF) used historically for executable content. This file format, which accommodates
MSIL or native code as well as metadata, enables the operating system to recognize common language runtime images. The presence of metadata in the file along with the MSIL enables your code to describe itself, which means that there is no need for type libraries or Interface Definition Language (IDL). The runtime locates and extracts the metadata from the file as needed during execution.
IL: (Intermediate Language)A language used as the output of a number of compilers and as the input to a just-in-time (JIT) compiler. The common language runtime includes a JIT compiler for converting MSIL to native code.
CTS: (Common Type System) The specification that determines how the common language runtime defines, uses, and manages types
CLR: (Common Language Runtime) The engine at the core of managed code execution. The runtime supplies managed code with services such as cross-language integration, code access security, object lifetime management, and debugging and profiling support.
Differnce between Managed code and unmanaged code ?
A: Managed Code: Code that runs under a “contract of cooperation” with the common language runtime. Managed code must supply the metadata necessary for the runtime to provide services such as memory management, cross-language integration, code access security, and automatic lifetime control of objects. All code based on Microsoft intermediate language (MSIL) executes as managed code.
Un-Managed Code:Code that is created without regard for the conventions and requirements of the common language runtime. Unmanaged code executes in the common language runtime environment with minimal services (for example, no garbage collection, limited debugging, and so on).
How can I stop my code being reverse-engineered from IL?
A: There is currently no simple way to stop code being reverse-engineered from IL. In future it is likely that IL obfuscation tools will become available, either from MS or from third parties. These tools work by ‘optimising’ the IL in such a way that reverse-engineering becomes much more difficult. Of course if you are writing web services then reverse-engineering is not a problem as clients do not have access to your IL.
Why is XmlSerializer so slow?
A: There is a once-per-process-per-type overhead with XmlSerializer. So the first time you serialize or deserialize an object of a given type in an application, there is a significant delay. This normally doesn’t matter, but it may mean, for example, that XmlSerializer is a poor choice for loading configuration settings during startup of a GUI application.
What are attributes?
A: There are at least two types of .NET attribute. The first type I will refer to as a metadata attribute - it allows some data to be attached to a class or method. This data becomes part of the metadata for the class, and (like other class metadata) can be accessed via reflection. The other type of attribute is a context attribute. Context attributes use a similar syntax to metadata attributes but they are fundamentally different. Context attributes provide an interception mechanism whereby instance activation and method calls can be
pre- and/or post-processed.
Can I customise the serialization process?
A: Yes. XmlSerializer supports a range of attributes that can be used to configure serialization for a particular class. For example, a field or property can be marked with the [XmlIgnore] attribute to exclude it from serialization. Another example is the [XmlElement]
attribute, which can be used to specify the XML element name to be used for a particular property or field.
Serialization via SoapFormatter/BinaryFormatter can also be controlled to some extent by attributes. For example, the [NonSerialized] attribute is the equivalent of XmlSerializer’s [XmlIgnore] attribute. Ultimate control of the serialization process can be acheived by implementing the the ISerializable interface on the class whose instances are to be serialized.
What is serialization?
A: Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization / Deserialization is mostly used to transport objects (e.g. during remoting), or to persist
objects (e.g. to a file or database).
Is the lack of deterministic destruction in .NET a problem?
A: It’s certainly an issue that affects component design. If you have objects that maintain expensive or scarce resources (e.g. database locks), you need to provide some way for the client to tell the object to release the resource when it is done. Microsoft recommend that you provide a method called Dispose() for this purpose. However, this causes problems for distributed objects - in a distributed system who calls the Dispose() method? Some form of reference-counting or ownership-management mechanism is needed to handle distributed objects - unfortunately the runtime offers no help with this.
Why doesn’t the .NET runtime offer deterministic destruction?
A: Because of the garbage collection algorithm. The .NET garbage collector works by periodically running through a list of all the objects that are currently being referenced by an application. All the objects that it doesn’t find during this search are ready to be destroyed and the memory reclaimed. The implication of this algorithm is that the runtime doesn’t get notified immediately when the final reference on an object goes away - it only finds out during the next sweep of the heap.
Futhermore, this type of algorithm works best by performing the garbage collection sweep as rarely as possible. Normally heap exhaustion is the trigger for a collection sweep.
What is side-by-side execution?
A: Can two application one using private assembly and other using Shared assembly be stated as a side-by-side executables? Side-by-side execution is the ability to run multiple versions of an application or component on the same computer. You can have multiple versions of the common language runtime, and multiple versions of applications and components that use a version of the runtime, on the same computer at the same time. Since versioning is only applied to shared assemblies, and not to private assemblies, two application one using private assembly and one using shared assembly cannot be stated as side-by-side
executables.
Why only boxed types can be unboxed?
A: Unboxing is the process of converting a Reference type variable to Value type and thus allocating memory on the stack . It happens only to those Reference type variables that have been earlier created by Boxing of a Value Type , therefore internally they contain a value type , which can be obtained through explicit casting . For any other Reference type , they don’t internally contain a Value type to Unboxed via explicit casting . This is why only boxed types can be unboxed .
What is the use of Internal keyword?
A: Internal keyword is one of the access specifier available in .Net framework , that makes a type visible in a given assembly , for e.g : a single dll can contain multiple modules , essentially a multi file assembly , but it forms a single binary component , so any type with internal keyword will be visible throughout the assembly and can be used in any of the modules .
Explain the differences between public, protected, private and internal.
A: These all are access modifier and they governs the access level. They can be applied to class, methods, fields.
Public: Allows class, methods, fields to be accessible from anywhere i.e. within and outside an assembly.
Private: When applied to field and method allows to be accessible within a class.
Protected: Similar to private but can be accessed by members of derived class also.
Internal: They are public within the assembly i.e. they can be accessed by anyone within an assembly but outside assembly they are not visible.
Explain the importance and use of each, Version, Culture and PublicKeyToken for an assembly.
A: This three alongwith name of the assembly provide a strong name or fully qualified name to the assembly. When a assebly is referenced with all three.
PublicKeyToken: Each assembly can have a public key embedded in its manifest that identifies the developer. This ensures that once the assembly ships, no one can modify the code or other resources contained in the assembly.
Culture: Specifies which culture the assembly supports
Version: The version number of the assembly.It is of the following form major.minor.build.revision.
What is FullTrust? Do GAC’ed assemblies have FullTrust?
A; fore the .NET Framework existed, Windows had two levels of trust for downloaded code. This old model was a binary trust model. You only had two choices: Full Trust, and No Trust. The code could either do anything you could do, or it wouldn’t run at all.
The permission sets in .NET include FullTrust, SkipVerification, Execution, Nothing, LocalIntranet, Internet and Everything. Full Trust Grants unrestricted permissions to system resources. Fully trusted code run by a normal, nonprivileged user cannot do administrative tasks, but can access any resources the user can access, and do anything the user can do. From a security standpoint, you can think of fully trusted code as being similar to native, unmanaged code, like a traditional ActiveX control.
GAC assemblies are granted FullTrust. In v1.0 and 1.1, the fact that assemblies in the GAC seem to always get a FullTrust grant is actually a side effect of the fact that the GAC lives on the local machine. If anyone were to lock down the security policy by changing the grant set of the local machine to something less than FullTrust, and if your assembly did not get extra permission from some other code group, it would no longer have FullTrust even though it lives in the GAC.
What are PDBs? Where must they be located for debugging to work?
A: A program database (PDB) files holds debugging and project state information that allows incremental linking of debug configuration of your program.There are several different types of symbolic debugging information. The default type for Microsoft compiler is the so-called PDB file. The compiler setting for creating this file is /Zi, or /ZI for C/C++(which creates a PDB file with additional information that enables a feature called “”Edit and Continue”") or a Visual Basic/C#/JScript .NET program with /debug.
A PDB file is a separate file, placed by default in the Debug project subdirectory, that has the same name as the executable file with the extension .pdb. Note that the Visual C++ compiler by default creates an additional PDB file called VC60.pdb for VisulaC++6.0 and VC70.PDB file for VisulaC++7.0. The compiler creates this file during compilation of the source code, when the compiler isn’t aware of the final name of the executable. The linker can merge this temporary PDB file into the main one if you tell it to, but it won’t do it by default. The PDB file can be useful to display the detailed stack trace with source files and line numbers.
How is the using() pattern useful? What is IDisposable? How does it support deterministic finalization?
A; The using() pattern is useful because it ensures that Dispose() will always be called when a disposable object (defined as one that implements IDisposable, and thus the Dispose() method) goes out of scope, even if it does so by an exception being thrown, and thus that resources are always released.
What is the difference between Finalize() and Dispose()?
A: Dispose() is called by the user of an object to indicate that he is finished with it, enabling that object to release any unmanaged resources it holds. Finalize() is called by the run-time to allow an object which has not had Dispose() called on it to do the same. However
Dispose() operates determinalistically, whereas there is no guarantee that Finalize() will be called immediately when an object goes out of scope - or indeed at all, if the program ends before that object is GCed - and as such Dispose() is generally preferred.
How does the generational garbage collector in the .NET CLR manage object lifetime?
What is non-deterministic finalization?
A: The hugely simplistic version is that every time it garbage-collects, it starts by assuming everything to be garbage, then goes through and builds a list of everything reachable. Those become not-garbage, everything else doesn’t, and gets thrown away. What makes it generational is that every time an object goes through this process and survives, it is noted as being a member of an older generation (up to 2, right now). When the garbage-collector is trying to free memory, it starts with the lowest generation (0) and only works up to higher ones if it can’t free up enough space, on the grounds that shorter-lived objects are more likely to have been freed than longer-lived ones.
Non-deterministic finalization implies that the destructor (if any) of an object will not necessarily be run (nor its memory cleaned up, but that’s a relatively minor issue) immediately upon its going out of scope. Instead, it will wait until first the garbage collector gets around to finding it, and then the finalisation queue empties down to it; and if the process ends before this happens, it may not be finalised at all. (Although the operating system will usually clean up any process-external resources left open - note the usually there, especially as the exceptions tend to hurt a lot.)
The PID (Process ID) a unique number for each item on the Process Tab, Image Name list. How do you get the PID to appear?
A: In Task Manger, select the View menu, then select columns and check PID (Process Identifier).In Linux, PID is used to debug a process explicitly. However we cannot do this in a windows environment.
Microsoft has launched a SDK called as Microsoft Operations Management (MOM). This uses the PID to find out which dll’s have been loaded by a process in the memory. This is essentially helpful in situations where the Process which has a memory leak is to be traced to a erring dll. Personally I have never used a PID, our Windows debugger does the things required to find out.
What is a PID? How is it useful when troubleshooting a system?
A: PID is the process Id of the application in Windows. Whenever a process starts running in the Windows environment, it is associated with an individual process Id or PID.
Describe the difference between a Thread and a Process?
A: A Process is an instance of an running application. And a thread is the Execution stream of the Process. A process can have multiple Thread.
When a process starts a specific memory area is allocated to it. When there is multiple thread in a process, each thread gets a memory for storing the variables in it and plus they can access to the global variables which is common for all the thread. Eg.A Microsoft Word is a Application. When you open a word file,an instance of the Word starts and a process is allocated to this instance which has one thread.
Difference between int and int32 ?
A: Both are same. System.Int32 is a .NET class. Int is an alias name for System.Int32.
Can a nested object be used in Serialization ?
A; Yes. If a class that is to be serialized contains references to objects of other classes, and if those classes have been marked as serializable, then their objects are serialized too.
Describe the advantages of writing a managed code application instead of unmanaged one. What’s involved in certain piece of code being managed?
A: “Advantage includes automatic garbage collection,memory management,security,type checking,versioning
Managed code is compiled for the .NET run-time environment. It runs in the Common Language Runtime (CLR), which is the heart of the .NET Framework. The CLR provides services such as security,memory management, and cross-language integration. Managed applications written to take advantage of the features of the CLR perform more efficiently and safely, and take better advantage of developers existing expertise in languages that support the .NET Framework.
Unmanaged code includes all code written before the .NET Framework was introduced—this includes code written to use COM, native Win32, and Visual Basic 6. Because it does not run inside the .NET environment, unmanaged code cannot make use of any .NET managed facilities.”
What is inline schema, how does it works?
A: Schemas can be included inside of XML file is called Inline Schemas.This is useful when it is inconvenient to physically seprate the schema and the XML document.A schema is an XML document that defines the structure, constraints, data types, and relationships of the elements that constitute the data contained inside the XML document or in another XML document.Schema can be an external file which uses the XSD or XDR extension called external schema. Inline schema can take place even when validation is turned off.
Why do you need to serialize.?
A: We need to serialize the object,if you want to pass object from one computer/application domain to another.Process of converting complex objects into stream of bytes that can be persisted or transported.Namespace for serialization is System.Runtime.Serialization.The ISerializable interface allows you to make any class Serializable..NET framework features 2 serializing method.
1.Binary Serialization
2.XML Serialization
What is GUID and why we need to use it and in what condition? How this is created.
A: A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated. Visual Studio .NET IDE has a utility under the tools menu to generate GUIDs.
What is encapsulation ?
A: Encapsulation is the ability to hide the internal workings of an object’s behavior and its data. For instance, let’s say you have a object named Bike and this object has a method named start(). When you create an instance of a Bike object and call its start() method you are not worried about what happens to accomplish this, you just want to make sure the state of the bike is changed to ‘running’ afterwards. This kind of behavior hiding is encapsulation and it makes programming much easier.
Difference between Dispose and Finallize method?
A: Finalize method is used to free the memory used by some unmanaged resources like window handles (HWND). It’s similar to the destructor syntax in C#. The GC calls this method when it founds no more references to the object. But, In some cases we may need release the memory used by the resources explicitely.To release the memory explicitly we need to implement the Dispose method of IDisposable interface.
Whate are Resource Files ? How are they used in .NET?
A: Resource files are the files containing data that is logically deployed with an application.These files can contain data in a number of formats including strings, images and persisted objects. It has the main advantage of If we store data in these files then we don’t need to compile these if the data get changed. In .NET we basically require them storing culture specific informations by localizing application’s resources. You can deploy your resources using satellite assemblies.
What is Globalizationa and Localization ?
A: Globalization is the process of creating an application that meets the needs of users from multiple cultures. It includes using the correct
currency, date and time format, calendar, writing direction, sorting rules, and other issues. Accommodating these cultural differences in an application is called localization.Using classes of System.Globalization namespace, you can set application’s current culture.
This can be achieved by using any of the following 3 approaches.
1.Detect and redirect
2.Run-time adjustment
3.Using Satellite assemblies.
What is managed and unmanaged code?
A: The .NET framework provides several core run-time services to the programs that run within it - for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. i.e., code executing under the control of the CLR is called managed code. For example, any code written in C# or Visual Basic .NET is managed code. Code that runs outside the CLR is referred to as “unmanaged code.” COM components, ActiveX components, and Win32 API functions are examples of unmanaged code.
What is the property available to check if the page posted or not?
A: The Page_Load event handler in the page checks for IsPostBack property value, to ascertain whether the page is posted. The Page.IsPostBack gets a value indicating whether the page is being loaded in response to the client postback, or it is for the first time. The value of Page.IsPostBack is True, if the page is being loaded in response to the client postback; while its value is False, when the page is loaded for the first time. The Page.IsPostBack property facilitates execution of certain routine in Page_Load, only once (for e.g. in Page load, we need to set default value in controls, when page is loaded for the first time. On post back, we check for true value for IsPostback value and then invoke server-side code to update data).
Changes to which portion of version number indicates an incompatible change?
A: Major or minor. Changes to the major or minor portion of the version number indicate an incompatible change. Under this convention then, version 2.0.0.0 would be considered incompatible with version 1.0.0.0. Examples of an incompatible change would be a change to the types of some method parameters or the removal of a type or method altogether. Build. The Build number is typically used to distinguish between daily builds or smaller compatible releases. Revision. Changes to the revision number are typically reserved for an incremental build needed to fix a particular bug. You’ll sometimes hear this referred to as the “emergency bug fix” number in that the revision is what is often changed when a fix to a specific bug is shipped to a customer.
What is Partial Assembly References?
A: Full Assembly reference: A full assembly reference includes the assembly’s text name, version, culture, and public key token (if the assembly has a strong name). A full assembly reference is required if you reference any assembly that is part of the common language runtime or any assembly located in the global assembly cache.
What is the difference between Finalize and Dispose (Garbage collection) ?
A: Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object. In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object.
Dispose can be called even if other references to the object are alive. Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from
permanently leaking if the programmer fails to call Dispose.
What is reflection?
A; All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember ) , or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).
What does ‘managed’ mean in the .NET context?
A: The term ‘managed’ is the cause of much confusion. It is used in various places within .NET, meaning slightly different things.Managed code: The .NET framework provides several core run-time services to the programs that run within it - for example
exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime.
Such code is called managed code. All C# and Visual Basic.NET code is managed by default. VS7 C++ code is not managed by default, but the compiler can produce managed code by specifying a command-line switch (/com+).
Managed data: This is data that is allocated and de-allocated by the .NET runtime’s garbage collector. C# and VB.NET data is always managed. VS7 C++ data is unmanaged by default, even when using the /com+ switch, but it can be marked as managed using the __gc keyword.Managed classes: This is usually referred to in the context of Managed Extensions (ME) for C++. When using ME C++, a class can be marked with the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector, but it also means more than that. The class becomes a fully paid-up member of the .NET community with the benefits and restrictions that brings. An example of a benefit is proper interop with classes written in other languages - for example, a managed C++ class can inherit from a VB class. An example of a restriction is that a managed class can only inherit from one base class.
What is IL?
A: IL = Intermediate Language. Also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code (of any language) is compiled to IL. The IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In-Time (JIT) compiler.
What is the CLS?
A: CLS = Common Language Specification. This is a subset of the CTS which all .NET languages are expected to support. The idea is that any program which uses CLS-compliant types can interoperate with any .NET program written in any language.
In theory this allows very tight interop between different .NET languages - for example allowing a C# class to inherit from a VB class.
What is the CTS?
A: CTS = Common Type System. This is the range of types that the .NET runtime understands, and therefore that .NET applications can use. However note that not all .NET languages will support all the types in the CTS. The CTS is a superset of the CLS.
What is the CLR?
A: CLR = Common Language Runtime. The CLR is a set of standard resources that (in theory) any .NET program can take advantage of, regardless of programming language. Robert Schmidt (Microsoft) lists the following CLR resources in his MSDN PDC# article:Object-oriented programming model (inheritance, polymorphism, exception handling, garbage collection) Security model Type system All .NET base classes
Many .NET framework classes Development, debugging, and profiling tools Execution and code management IL-to-native translators and optimizers What this means is that in the .NET world, different programming languages will be more equal in capability than they have ever been before, although clearly not all languages will support all CLR services.
When was the first version of .NET released?
A: The final version of the 1.0 SDK and runtime was made publicly available around 6pm PST on 15-Jan-2002. At the same time, the final version of Visual Studio.NET was made available to MSDN subscribers.
When was .NET announced?
A: Bill Gates delivered a keynote at Forum 2000, held June 22, 2000, outlining the .NET ‘vision’. The July 2000 PDC had a number of sessions on .NET technology, and delegates were given CDs containing a pre-release version of the .NET framework/SDK and Visual Studio.NET.
What happens in memory when you Box and Unbox a value-type?
A: Boxing converts a value-type to a reference-type, thus storing the object on the heap. Unboxing converts a reference-type to a value-type, thus storing the value on the stack.
When should you call the garbage collector in .NET?
A: As a good rule, you should not call the garbage collector. However, you could call the garbage collector when you are done using a large object (or set of objects) to force the garbage collector to dispose of those very large objects from memory. However, this is usually not a good practice.
What is a satellite assembly?
A: When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is the DLL Hell problem solved in .NET?
A: Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
How you will set the datarelation between two columns?
A: ADO.NET provides DataRelation object to set relation between two columns.It helps to enforce the following constraints,a unique constraint, which guarantees that a column in the table contains no duplicates and a foreign-key constraint,which can be used to maintain referential integrity.A unique constraint is implemented either by simply setting the Unique property of a data column to true, or by adding an instance of the UniqueConstraint class to the DataRelation object’s ParentKeyConstraint. As part of the foreign-key constraint, you can specify referential integrity rules that are applied at three points,when a parent record is updated,when a parent record is deleted and when a change is accepted or rejected.
Is Your Glass Half Full?
A; There are three common techniques for managing what happens when users try to modify the same data at the same time: pessimistic, optimistic, and last-in wins. They each handle concurrency issues differently.
The pessimistic approach says: “Nobody can cause a concurrency violation with my data if I do not let them get at the data while I have it.” This tactic prevents concurrency in the first place but it limits scalability because it prevents all concurrent access. Pessimistic concurrency generally locks a row from the time it is retrieved until the time updates are flushed to the database. Since this requires a connection to remain open during the entire process, pessimistic concurrency cannot successfully be implemented in a disconnected model like the ADO.NET DataSet, which opens a connection only long enough to populate the DataSet then releases and closes, so a database lock cannot be held.
Another technique for dealing with concurrency is the last-in wins approach. This model is pretty straightforward and easy to implement-whatever data modification was made last is what gets written to the database. To implement this technique you only need to put the primary key fields of the row in the UPDATE statement’s WHERE clause. No matter what is changed, the UPDATE statement will overwrite the changes with its own changes since all it is looking for is the row that matches the primary key values. Unlike the pessimistic model, the last-in wins approach allows users to read the data while it is being edited on screen. However, problems can occur when users try to modify the same data at the same time because users can overwrite each other’s changes without being notified of the collision. The last-in wins approach does not detect or notify the user of violations because it does not care. However the optimistic technique does detect violations.
In optimistic concurrency models, a row is only locked during the update to the database. Therefore the data can be retrieved and updated by other users at any time other than during the actual row update operation. Optimistic concurrency allows the data to be read simultaneously by multiple users and blocks other users less often than its pessimistic counterpart, making it a good choice for ADO.NET. In optimistic models, it is important to implement some type of concurrency violation detection that will catch any additional attempt to modify records that have already been modified but not committed. You can write your code to handle the violation by always rejecting and canceling the change request or by overwriting the request based on some business rules. Another way to handle the concurrency violation is to let the user decide what to do. The sample application that is shown in Figure 1 illustrates some of the options that can be presented to the user in the event of a concurrency violation.
Explain the ADO . Net Architecture ( .Net Data Provider)
A: ADO.Net is the data access model for .Net –based applications. It can be used to access relational database systems such as SQL SERVER 2000, Oracle, and many other data sources for which there is an OLD DB or ODBC provider. To a certain extent, ADO.NET represents the latest evolution of ADO technology. However, ADO.NET introduces some major changes and innovations that are aimed at the loosely coupled and inherently disconnected – nature of web applications.
A .Net Framework data provider is used to connecting to a database, executing commands, and retrieving results. Those results are either processed directly, or placed in an ADO.NET DataSet in order to be exposed to the user in an ad-hoc manner, combined with data from multiple sources, or remoted between tiers. The .NET Framework data provider is designed to be lightweight, creating a minimal layer between the data source and your code, increasing performance without sacrificing functionality.
Following are the 4 core objects of .Net Framework Data provider:
• Connection: Establishes a connection to a specific data source
• Command: Executes a command against a data source. Exposes Parameters and can execute within the scope of a Transaction from a Connection.
• DataReader: Reads a forward-only, read-only stream of data from a data source.
• DataAdapter: Populates a DataSet and resolves updates with the data source.
The .NET Framework includes the .NET Framework Data Provider for SQL Server (for Microsoft SQL Server version 7.0 or later), the .NET Framework Data Provider for OLE DB, and the .NET Framework Data Provider for ODBC.
The .NET Framework Data Provider for SQL Server: The .NET Framework Data Provider for SQL Server uses its own protocol to communicate with SQL Server. It is lightweight and performs well because it is optimized to access a SQL Server directly without adding an OLE DB or Open Database Connectivity (ODBC) layer. The following illustration contrasts the .NET Framework Data Provider for SQL Server with the .NET Framework Data Provider for OLE DB. The .NET Framework Data Provider for OLE DB communicates to an OLE DB data source through both the OLE DB Service component, which provides connection pooling and transaction services, and the OLE DB Provider for the data source
The .NET Framework Data Provider for OLE DB: The .NET Framework Data Provider for OLE DB uses native OLE DB through COM interoperability to enable data access. The .NET Framework Data Provider for OLE DB supports both local and distributed transactions. For distributed transactions, the .NET Framework Data Provider for OLE DB, by default, automatically enlists in a transaction and obtains transaction details from Windows 2000 Component Services.
The .NET Framework Data Provider for ODBC: The .NET Framework Data Provider for ODBC uses native ODBC Driver Manager (DM) through COM interoperability to enable data access. The ODBC data provider supports both local and distributed transactions. For distributed transactions, the ODBC data provider, by default, automatically enlists in a transaction and obtains transaction details from Windows 2000 Component Services.
The .NET Framework Data Provider for Oracle: The .NET Framework Data Provider for Oracle enables data access to Oracle data sources through Oracle client connectivity software. The data provider supports Oracle client software version 8.1.7 and later. The data provider supports both local and distributed transactions (the data provider automatically enlists in existing distributed transactions, but does not currently support the EnlistDistributedTransaction method).
The .NET Framework Data Provider for Oracle requires that Oracle client software (version 8.1.7 or later) be installed on the system before you can use it to connect to an Oracle data source.
.NET Framework Data Provider for Oracle classes are located in the System.Data.OracleClient namespace and are contained in the System.Data.OracleClient.dll assembly. You will need to reference both the System.Data.dll and the System.Data.OracleClient.dll when compiling an application that uses the data provider.
Choosing a .NET Framework Data Provider
.NET Framework Data Provider for SQL Server: Recommended for middle-tier applications using Microsoft SQL Server 7.0 or later. Recommended for single-tier applications using Microsoft Data Engine (MSDE) or Microsoft SQL Server 7.0 or later.
Recommended over use of the OLE DB Provider for SQL Server (SQLOLEDB) with the .NET Framework Data Provider for OLE DB. For Microsoft SQL Server version 6.5 and earlier, you must use the OLE DB Provider for SQL Server with the .NET Framework Data Provider for OLE DB.
.NET Framework Data Provider for OLE DB: Recommended for middle-tier applications using Microsoft SQL Server 6.5 or earlier, or any OLE DB provider. For Microsoft SQL Server 7.0 or later, the .NET Framework Data Provider for SQL Server is recommended. Recommended for single-tier applications using Microsoft Access databases. Use of a Microsoft Access database for a middle-tier application is not recommended.
.NET Framework Data Provider for ODBC: Recommended for middle-tier applications using ODBC data sources. Recommended for single-tier applications using ODBC data sources.
.NET Framework Data Provider for Oracle: Recommended for middle-tier applications using Oracle data sources. Recommended for single-tier applications using Oracle data sources. Supports Oracle client software version 8.1.7 and later. The .NET Framework Data Provider for Oracle classes are located in the System.Data.OracleClient namespace and are contained in the System.Data.OracleClient.dll assembly. You need to reference both the System.Data.dll and the System.Data.OracleClient.dll when compiling an application that uses the data provider.
Explain acid properties?.
A: The term ACID conveys the role transactions play in mission-critical applications. Coined by transaction processing pioneers, ACID stands for atomicity, consistency, isolation, and durability.
These properties ensure predictable behavior, reinforcing the role of transactions as all-or-none propositions designed to reduce the management load when there are many variables.
Atomicity
A transaction is a unit of work in which a series of operations occur between the BEGIN TRANSACTION and END TRANSACTION statements of an application. A transaction executes exactly once and is atomic — all the work is done or none of it is.
Operations associated with a transaction usually share a common intent and are interdependent. By performing only a subset of these operations, the system could compromise the overall intent of the transaction. Atomicity eliminates the chance of processing a subset of operations.
Consistency
A transaction is a unit of integrity because it preserves the consistency of data, transforming one consistent state of data into another consistent state of data.
Consistency requires that data bound by a transaction be semantically preserved. Some of the responsibility for maintaining consistency falls to the application developer who must make sure that all known integrity constraints are enforced by the application. For example, in developing an application that transfers money, you should avoid arbitrarily moving decimal points during the transfer.
Isolation
A transaction is a unit of isolation — allowing concurrent transactions to behave as though each were the only transaction running in the system.
Isolation requires that each transaction appear to be the only transaction manipulating the data store, even though other transactions may be running at the same time. A transaction should never see the intermediate stages of another transaction.
Transactions attain the highest level of isolation when they are serializable. At this level, the results obtained from a set of concurrent transactions are identical to the results obtained by running each transaction serially. Because a high degree of isolation can limit the number of concurrent transactions, some applications reduce the isolation level in exchange for better throughput.
Durability
A transaction is also a unit of recovery. If a transaction succeeds, the system guarantees that its updates will persist, even if the computer crashes immediately after the commit. Specialized logging allows the system’s restart procedure to complete unfinished operations, making the transaction durable.
What is a pre-requisite for connection pooling?
A; Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical.
Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted?
A; Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
What is the wildcard character in SQL?
A: Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’
What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
A; SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. OLE-DB.NET is a .NET layer on top of the OLE layer, so it’s not as fastest and efficient as SqlServer.NET.
What is the role of the DataReader class in ADO.NET connections?
A: It returns a read-only, forward-only rowset from the data source. A DataReader provides fast access when a forward-only sequential read is needed.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
A: The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels range from None to Verbose, allowing you to fine-tune the tracing activities.
What does assert() method do?
A: In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
Can you declare an override method to be static if the original method is not static?
A: No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)
How is method overriding different from method overloading?
A: When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class
What is the difference between a Struct and a Class?
A: Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
What’s the difference between an interface and abstract class?
A: In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
What happens if you inherit multiple interfaces and they have conflicting method names?
A: It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
To Do: Investigate
Explain the three services model commonly know as a three-tier application.
A: Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
Can multiple catch blocks be executed for a single try statement?
A: No. Once the proper catch block processed, control is transferred to the finally block (if there are any)
What’s the C# syntax to catch any possible exception?
A: A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
A: The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element’s object, resulting in a different, yet identacle object.
What’s the advantage of using System.Text.StringBuilder over System.String?
A: StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.
What does the term immutable mean?
A: The data value may not be changed. Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
Are private class-level variables inherited?
A: Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
Who is a protected class-level variable available to?
A: It is available to any sub-class (a class inheriting this class).
What is a Windows Service and how does its lifecycle differ from a “standard” EXE?
A: Windows service is a application that runs in the background. It is equivalent to a NT service.
The executable created is not a Windows application, and hence you can’t just click and run it . it needs to be installed as a service, VB.Net has a facility where we can add an installer to our program and then use a utility to install the service. Where as this is not the case with standard exe
Can you create an app domain?
A; Yes, We can create user app domain by calling on of the following overload static methods of the System.AppDomain class
1. Public static AppDomain CreateDomain(String friendlyName)
2. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo)
3. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info)
4. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, String appBasePath, String appRelativeSearchPath, bool shadowCopyFiles)
What is the difference between Server.Transfer and Response.Redirect?
A: Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist across the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.
Response.Dedirect() :client knows the physical location (page name and query string as well). Context.Items loses the persistence when navigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites,
What does the term immutable mean?
A: The data value may not be changed. Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
Are private class-level variables inherited?
A: Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
Who is a protected class-level variable available to?
A: It is available to any sub-class (a class inheriting this class).
What is a Windows Service and how does its lifecycle differ from a “standard” EXE?
A: Windows service is a application that runs in the background. It is equivalent to a NT service.
The executable created is not a Windows application, and hence you can’t just click and run it . it needs to be installed as a service, VB.Net has a facility where we can add an installer to our program and then use a utility to install the service. Where as this is not the case with standard exe
Can you create an app domain?
A; Yes, We can create user app domain by calling on of the following overload static methods of the System.AppDomain class
1. Public static AppDomain CreateDomain(String friendlyName)
2. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo)
3. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info)
4. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, String appBasePath, String appRelativeSearchPath, bool shadowCopyFiles)
What is the difference between Server.Transfer and Response.Redirect?
A: Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist across the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.
Response.Dedirect() :client knows the physical location (page name and query string as well). Context.Items loses the persistence when navigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
Response.Redirect sends a response to the client browser instructing it to request the second page. This requires a round-trip to the client, and the client initiates the Request for the second page. Server.Transfer transfers the process to the second page without making a round-trip to the client. It also transfers the HttpContext to the second page, enabling the second page access to all the values in the HttpContext of the first page.
How do you implement Paging in .Net?
A: The DataGrid provides the means to display a group of records from the data source (for example, the first 10), and then navigate to the “page” containing the next 10 records, and so on through the data.
Using Ado.Net we can explicit control over the number of records returned from the data source, as well as how much data is to be cached locally in the DataSet.
1.Using DataAdapter.fill method give the value of ‘Maxrecords’ parameter (Note: - Don’t use it because query will return all records but fill the dataset based on value of ‘maxrecords’ parameter).
2.For SQL server database, combines a WHERE clause and a ORDER BY clause with TOP predicate.
3.If Data does not change often just cache records locally in DataSet and just take some records from the DataSet to display.
What is the difference between HTTP-Post and HTTP-Get?
A: As their names imply, both HTTP GET and HTTP POST use HTTP as their underlying protocol. Both of these methods encode request parameters as name/value pairs in the HTTP request.
The GET method creates a query string and appends it to the script’s URL on the server that handles the request.
The POST method creates a name/value pairs that are passed in the body of the HTTP request message.
What is the difference between in-proc and out-of-proc?
A: An inproc is one which runs in the same process area as that of the client giving tha advantage of speed but the disadvantage of stability becoz if it crashes it takes the client application also with it.Outproc is one which works outside the clients memory thus giving stability to the client, but we have to compromise a bit on speed.
What are the various ways of securing a web site that could prevent from hacking etc .. ?
A: 1) Authentication/Authorization
2) Encryption/Decryption
3) Maintaining web servers outside the corporate firewall. etc.,
What is validationsummary server control?where it is used?.
A: The ValidationSummary control allows you to summarize the error messages from all validation controls on a Web page in a single location. The summary can be displayed as a list, a bulleted list, or a single paragraph, based on the value of the DisplayMode property. The error message displayed in the ValidationSummary control for each validation control on the page is specified by the ErrorMessage property of each validation control. If the ErrorMessage property of the validation control is not set, no error message is displayed in the ValidationSummary control for that validation control. You can also specify a custom title in the heading section of the ValidationSummary control by setting the HeaderText property. You can control whether the ValidationSummary control is displayed or hidden by setting the ShowSummary property. The summary can also be displayed in a message box by setting the ShowMessageBox property to true.
What is ViewState ? and how it is managed ?
A: ASP.NET ViewState is a new kind of state service that developers can use to track UI state on a per-user basis. Internally it uses an an old Web programming trick-roundtripping state in a hidden form field and bakes it right into the page-processing framework.It needs less code to write and maintain state in your Web-based forms.
What are different templates available in Repeater,DataList and Datagrid ?
A: Templates enable one to apply complicated formatting to each of the items displayed by a control.Repeater control supports five types of templates.HeaderTemplate controls how the header of the repeater control is formatted.ItemTemplate controls the formatting of each item displayed.AlternatingItemTemplate controls how alternate items are formatted and the SeparatorTemplate displays a separator between each item displyed.FooterTemplate is used for controlling how the footer of the repeater control is formatted.The DataList and Datagrid supports two templates in addition to the above five.SelectedItem Template controls how a selected item is formatted and EditItemTemplate controls how an item selected for editing is formatted.
” ?">When do you set “” ?
A: Identity is a webconfig declaration under System.web, which helps to control the application Identity of the web applicaton. Which can be at any level (Machine,Site, application, subdirectory , or page) , attribute impersonate with “true” as value specifies that client impersonation is used.
How do you register JavaScript for webcontrols ?
A: You can register javascript for controls using Attribtues.Add(scriptname,scripttext) method.
Which two properties are on every validation control?
A: We have two common properties for every validation controls
1. Control to Validate,
2. Error Message.
How do you create a permanent cookie?
A; Permanent cookies are the ones that are most useful. Permanent cookies are available until a specified expiration date, and are stored on the hard disk. The location of cookies differs with each browser, but this doesn’t matter, as this is all handled by your browser and the server. If you want to create a permanent cookie called Name with a value of Nigel, which expires in one month, you’d use the following code
Response.Cookies (”Name”) = “Nigel” Response.Cookies (”Name”). Expires = DateAdd (”m”, 1, Now ())
How do you turn off cookies for one page in your site?
A: Use Cookie.Discard property, Gets or sets the discard flag set by the server. When true, this property instructs the client application not to save the Cookie on the user’s hard disk when a session ends.
What method do you use to explicitly kill a user s session?
A: You can dump (Kill) the session yourself by calling the method Session.Abandon.
ASP.NET automatically deletes a user’s Session object, dumping its contents, after it has been idle for a configurable timeout interval. This interval, in minutes, is set in the section of the web.config file. The default is 20 minutes.
What are the advantages and disadvantages of viewstate?
A: The primary advantages of the ViewState feature in ASP.NET are:
1. Simplicity. There is no need to write possibly complex code to store form data between page submissions.
2. Flexibility. It is possible to enable, configure, and disable ViewState on a control-by-control basis, choosing to persist the values of some fields but not others.
There are, however a few disadvantages that are worth pointing out:
1. Does not track across pages. ViewState information does not automatically transfer from page to page. With the session approach, values can be stored in the session and accessed from other pages. This is not possible with ViewState, so storing data into the session must be done explicitly.
2. ViewState is not suitable for transferring data for back-end systems. That is, data still has to be transferred to the back end using some form of data object.
Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?
A: The Application_Start event is guaranteed to occur only once throughout the lifetime of the application. It’s a good place to initialize global variables. For example, you might want to retrieve a list of products from a database table and place the list in application state or the Cache object. SessionStateModule exposes both Session_Start and Session_End events.
Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component?
A: Communicating through a Firewall When building a distributed application with 100s/1000s of users spread over multiple locations, there is always the problem of communicating between client and server because of firewalls and proxy servers. Exposing your middle tier components as Web Services and invoking the directly from a Windows UI is a very valid option.
• Application Integration When integrating applications written in various languages and running on disparate systems. Or even applications running on the same platform that have been written by separate vendors.
• Business-to-Business Integration This is an enabler for B2B intergtation which allows one to expose vital business processes to authorized supplier and customers. An example would be exposing electronic ordering and invoicing, allowing customers to send you purchase orders and suppliers to send you invoices electronically.
• Software Reuse This takes place at multiple levels. Code Reuse at the Source code level or binary componet-based resuse. The limiting factor here is that you can reuse the code but not the data behind it. Webservice overcome this limitation. A scenario could be when you are building an app that aggregates the functionality of serveral other Applicatons. Each of these functions could be performed by individual apps, but there is value in perhaps combining the the multiple apps to present a unifiend view in a Portal or Intranet.
•When not to use Web Services: Single machine Applicatons When the apps are running on the same machine and need to communicate with each other use a native API. You also have the options of using component technologies such as COM or .NET Componets as there is very little overhead.
•Homogeneous Applications on a LAN If you have Win32 or Winforms apps that want to communicate to their server counterpart. It is much more efficient to use DCOM in the case of Win32 apps and .NET Remoting in the case of .NET Apps
What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
A: Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist accros the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.
Response.Dedirect() :client know the physical location (page name and query string as well). Context.Items loses the persisitance when nevigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
What does the “EnableViewState” property do? Why would I want it on or off?
A: Enable ViewState turns on the automatic state management feature that enables server controls to re-populate their values on a round trip without requiring you to write any code. This feature is not free however, since the state of a control is passed to and from the server in a hidden form field. You should be aware of when ViewState is helping you and when it is not. For example, if you are binding a control to data on every round trip, then you do not need the control to maintain it’s view state, since you will wipe out any re-populated data in any case. ViewState is enabled for all server controls by default. To disable it, set the EnableViewState property of the control to false.
Should validation (did the user enter a real date) occur server-side or client-side? Why?
A: It should occur both at client-side and Server side.By using expression validator control with the specified expression ie.. the regular expression provides the facility of only validatating the date specified is in the correct format or not. But for checking the date where it is the real data or not should be done at the server side, by getting the system date ranges and checking the date whether it is in between that range or not.
How do you create a permanent cookie?
A: Permanent cookies are available until a specified expiration date, and are stored on the hard disk.So Set the ‘Expires’ property any value greater than DataTime.MinValue with respect to the current datetime. If u want the cookie which never expires set its Expires property equal to DateTime.maxValue.
What is different b/w webconfig.xml & Machineconfig.xml
A: Web.config & machine.config both are configuration files.Web.config contains settings specific to an application where as machine.config contains settings to a computer. The Configuration system first searches settings in machine.config file & then looks in application configuration files.Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies configuration settings to its own directory and all child directories below it. There is only Machine.config file on a web server.
If I’m developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is spanned across three web-servers (using round-robbin load balancing) what would be the best approach to maintain login-in state for the users?
Use the state server or store the state in the database. This can be easily done through simple setting change in the web.config.
StateConnectionString="tcpip=127.0.0.1:42424"
sqlConnectionString="data source=127.0.0.1; user id=sa; password="
cookieless="false"
timeout="30" />
You can specify mode as “stateserver” or “sqlserver”.
Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one
“One of ASP.NET’s most useful features is the extensibility of the HTTP pipeline, the path that data takes between client and server. You can use them to extend your ASP.NET applications by adding pre- and post-processing to each HTTP request coming into your application. For example, if you wanted custom authentication facilities for your application, the best technique would be to intercept the request when it comes in and process the request in a custom HTTP module.
What event handlers can I include in Global.asax?
A: Application_Start,Application_End, Application_AcquireRequestState, Application_AuthenticateRequest, Application_AuthorizeRequest, Application_BeginRequest, Application_Disposed, Application_EndRequest, Application_Error, Application_PostRequestHandlerExecute, Application_PreRequestHandlerExecute,
Application_PreSendRequestContent, Application_PreSendRequestHeaders, Application_ReleaseRequestState, Application_ResolveRequestCache, Application_UpdateRequestCache, Session_Start,Session_End
You can optionally include “On” in any of method names. For example, you can name a BeginRequest event handler.Application_BeginRequest or Application_OnBeginRequest.You can also include event handlers in Global.asax for events fired by custom HTTP modules.Note that not all of the event handlers make sense for Web Services (they’re designed for ASP.NET applications in general, whereas .NET XML Web Services are specialized instances of an ASP.NET app). For example, the Application_AuthenticateRequest and Application_AuthorizeRequest events are designed to be used with ASP.NET Forms authentication.
How can you provide an alternating color scheme in a Repeater control?
A: AlternatingItemTemplate Like the ItemTemplate element, but rendered for every other row (alternating items) in the Repeater control. You can specify a different appearance for the AlternatingItemTemplate element by setting its style properties.
What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
A: In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems.
As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
What are ASP.NET Web Forms? How is this technology different than what is available though ASP?
A: Web Forms are the heart and soul of ASP.NET. Web Forms are the User Interface (UI) elements that give your Web applications their look and feel. Web Forms are similar to Windows Forms in that they provide properties, methods, and events for the controls that are placed onto them. However, these UI elements render themselves in the appropriate markup language required by the request, e.g. HTML. If you use Microsoft Visual Studio .NET, you will also get the familiar drag-and-drop interface used to create your UI for your Web application.
What type of code (server or client) is found in a Code-Behind class?
A: Client-side validation because there is no need to request a server side date when you could obtain a date from the client machine.
Explain the differences between Server-side and Client-side code?
A: Server side scripting means that all the script will be executed by the server and interpreted as needed. ASP doesn’t have some of the functionality like sockets, uploading, etc. For these you have to make a custom components usually in VB or VC++. Client side scripting means that the script will be executed immediately in the browser such as form field validation, clock, email validation, etc. Client side scripting is usually done in VBScript or JavaScript. Download time, browser compatibility, and visible code - since JavaScript and VBScript code is included in the HTML page, then anyone can see the code by viewing the page source. Also a possible security hazards for the client computer.
What does AspCompat=”true” mean and when should I use it?
A: AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects–that is, COM objects registered ThreadingModel=Apartment. That includes all COM objects written with Visual Basic 6.0. AspCompat should also be set to true (regardless of threading model) if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true:
Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available to the COM components by placing unmanaged wrappers around the equivalent ASP.NET objects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the request for the page) and the COM objects it creates share an apartment. AspCompat=”true” forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel=Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat=”true,” request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it’s marshaled across apartment boundaries.
Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don’t access ASP intrinsic objects and that are registered ThreadingModel=Free or ThreadingModel=Both.
How does dynamic discovery work?
A: ASP.NET maps the file name extension VSDISCO to an HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document. A client who requests a VSDISCO file gets back what appears to be a static DISCO document.
Note that VSDISCO files are disabled in the release version of ASP.NET. You can reenable them by uncommenting the line in the section of Machine.config that maps *.vsdisco to System.Web.Services.Discovery.DiscoveryRequestHandler and granting the ASPNET user account permission to read the IIS metabase. However, Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security.
How do I send e-mail from an ASP.NET application?
A: MailMessage message = new MailMessage ();
message.From = ;
message.To = ;
message.Subject = “Scheduled Power Outage”;
message.Body = “Our servers will be down tonight.”;
SmtpMail.SmtpServer = “localhost”;
SmtpMail.Send (message);
MailMessage and SmtpMail are classes defined in the .NET Framework Class Library’s System.Web.Mail namespace. Due to a security change made to ASP.NET just before it shipped, you need to set SmtpMail’s SmtpServer property to “localhost” even though “localhost” is the default. In addition, you must use the IIS configuration applet to enable localhost (127.0.0.1) to relay messages through the local SMTP service.
Is it necessary to lock application state before accessing it?
A: Only if you’re performing a multistep update and want the update to be treated as an atomic operation. Here’s an example:
Application.Lock ();
Application[”ItemsSold”] = (int) Application[”ItemsSold”] + 1;
Application[”ItemsLeft”] = (int) Application[”ItemsLeft”] - 1;
Application.UnLock ();
By locking application state before updating it and unlocking it afterwards, you ensure that another request being processed on another thread doesn’t read application state at exactly the wrong time and see an inconsistent view of it. If I update session state, should I lock it, too? Are concurrent accesses by multiple requests executing on multiple threads a concern with session state? Concurrent accesses aren’t an issue with session state, for two reasons. One, it’s unlikely that two requests from the same user will overlap. Two, if they do overlap, ASP.NET locks down session state during request processing so that two threads can’t touch it at once. Session state is locked down when the HttpApplication instance that’s processing the request fires an AcquireRequestState event and unlocked when it fires a ReleaseRequestState event.
Can a user browsing my Web site read my Web.config or Global.asax files?
A: No. The section of Machine.config, which holds the master configuration settings for ASP.NET, contains entries that map ASAX files, CONFIG files, and selected other file types to an HTTP handler named HttpForbiddenHandler, which fails attempts to retrieve the associated file. You can modify it by editing Machine.config or including an section in a local Web.config file.
How do I debug an ASP.NET application that wasn’t written with Visual Studio.NET and that doesn’t use code-behind?
A: Start the DbgClr debugger that comes with the .NET Framework SDK, open the file containing the code you want to debug, and set your breakpoints. Start the ASP.NET application. Go back to DbgClr, choose Debug Processes from the Tools menu, and select aspnet_wp.exe from the list of processes. (If aspnet_wp.exe doesn’t appear in the list,check the “Show system processes” box.) Click the Attach button to attach to aspnet_wp.exe and begin debugging.
Be sure to enable debugging in the ASPX file before debugging it with DbgClr. You can enable tell ASP.NET to build debug executables by placing a
statement at the top of an ASPX file or a statement in a Web.config file.
What are different types of directives in .NET?
A: @Page: Defines page-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .aspx files
@Control:Defines control-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .ascx files.
@Import: Explicitly imports a namespace into a page or user control. The Import directive cannot have more than one namespace attribute. To import multiple namespaces, use multiple @Import directives.
@Implements: Indicates that the current page or user control implements the specified .NETframework interface.
@Register: Associates aliases with namespaces and class names for concise notation in custom server control syntax.
@Assembly: Links an assembly to the current page during compilation, making all the assembly’s classes and interfaces available for use on the page.
@OutputCache: Declaratively controls the output caching policies of an ASP.NET page or a user control contained in a page
@Reference: Declaratively indicates that another user control or page source file should be dynamically compiled and linked against the page in which this directive is declared.
What do you mean by authentication and authorization?
A: Authentication is the process of validating a user on the credentials (username and password) and authorization performs after authentication. After Authentication a user will be verified for performing the various tasks, Its access is limited it is known as authorization.
What are the different types of caching?
A: Caching is a technique widely used in computing to increase performance by keeping frequently accessed or expensive data in memory. In context of web application, caching is used to retain the pages or data across HTTP requests and reuse them without the expense of recreating them. ASP.NET has 3 kinds of caching strategies Output Caching, Fragment Caching, Data Caching.
Output Caching: Caches the dynamic output generated by a request. Some times it is useful to cache the output of a website even for a minute, which will result in a better performance. For caching the whole page the page should have OutputCache directive.
Fragment Caching: Caches the portion of the page generated by the request. Some times it is not practical to cache the entire page, in such cases we can cache a portion of page
Data Caching: Caches the objects programmatically. For data caching asp.net provides a cache object for eg: cache[”States”] = dsStates;
What methods are fired during the page load?
A: Init() When the page is instantiated, Load() - when the page is loaded into server memory,PreRender () - the brief moment before the page is displayed to the user as HTML, Unload() - when page finishes loading.
What is view state and use of it?
A: The current property settings of an ASP.NET page and those of any ASP.NET server controls contained within the page. ASP.NET can detect when a form is requested for the first time versus when the form is posted (sent to the server), which allows you to program accordingly.
What are the validation controls?
A: set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation using client script.
What are user controls and custom controls?
A: Custom controls: A control authored by a user or a third-party software vendor that does not belong to the .NET Framework class library. This is a generic term that includes user controls. A custom server control is used in Web Forms (ASP.NET pages). A custom client control is used in Windows Forms applications.
User Controls: In ASP.NET: A user-authored server control that enables an ASP.NET page to be re-used as a server control. An ASP.NET user control is authored declaratively and persisted as a text file with an .ascx extension. The ASP.NET page framework compiles a user control on the fly to a class that derives from the System.Web.UI.UserControl class.
What are the different types of assemblies available and their purpose?
A: Private, Public/shared and Satellite Assemblies.
Private Assemblies : Assembly used within an application is known as private assemblies.
Public/shared Assemblies : Assembly which can be shared across applicaiton is known as shared assemblies. Strong Name has to be created to create a shared assembly. This can be done using SN.EXE. The same has to be registered using GACUtil.exe (Global Assembly Cache).
What is the difference between Value Types and Reference Types?
A: Value Types uses Stack to store the data where as the later uses the Heap to store the data.
What is Boxing and UnBoxing?
A: Boxing is implicit conversion of ValueTypes to Reference Types (Object). UnBoxing is explicit conversion of Reference Types (Object) to its equivalent ValueTypes. It requires type-casting.
What are the different types of Session state management options available with ASP.NET?
A: ASP.NET provides In-Process and Out-of-Process state management. In-Process stores the session in memory on the web server. This requires the a “sticky-server” (or no load-balancing) so that the user is always reconnected to the same web server. Out-of-Process Session state management stores data in an external data source. The external data source may be either a SQL Server or a State Server service. Out-of-Process state management requires that all objects stored in session are serializable.
What does the “EnableViewState” property do? Why would I want it on or off?
A: It allows the page to save the users input on a form across postbacks. It saves the server-side values for a given control into ViewState, which is stored as a hidden value on the page before sending the page to the clients browser. When the page is posted back to the server the server control is recreated with the state stored in viewstate.
What is the lifespan for items stored in ViewState?
A: Item stored in ViewState exist for the life of the current page. This includes postbacks (to the same page).
What is ViewState?
A: ViewState allows the state of objects (serializable) to be stored in a hidden field on the page. ViewState is transported to the client and back to the server, and is not stored on the server or any other external source. ViewState is used to retain the state of server-side objects between post backs.
Can you edit data in the Repeater control?
A: No, it just reads the information from its data source.
Which method do you invoke on the DataAdapter control to load your generated dataset with data?
A: The Fill() method.
Whats MSIL, and why should my developers need an appreciation of it if at all?
A: MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL. MSIL also allows the .NET Framework to JIT compile the assembly on the installed computer.
Explain what a diffgram is, and a good use for one?
A: The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML. A good use is reading database data to an XML file to be sent to a Web Service.
Describe the difference between inline and code behind.
A: Inline code written along side the html in a page. Code-behind is code written in a separate file and referenced by the .aspx page
Can you explain what inheritance is and an example of when you might use it?
A: When you want to inherit (use the functionality of) another class. Example: With a base class named Employee, a Manager class could be derived from the Employee base class.
What are the Application_Start and Session_Start subroutines used for?
A: This is where you can set the specific variables for the Application and Session objects
What is the Global.asax used for?
A: The Global.asax (including the Global.asax.cs file) is used to implement application and session level events.
Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
A: Valid answers are:
• A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
• A DataSet is designed to work without any continuing connection to the original data source.
• Data in a DataSet is bulk-loaded, rather than being loaded on demand.
• There’s no concept of cursor types in a DataSet.
• DataSets have no current record pointer You can use For Each loops to move through the data.
• You can store many edits in a DataSet, and write them to the original data source in a single operation.
• Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.
What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
A: Server.Transfer transfers page processing from one page directly to the next page without making a round-trip back to the client’s browser. This provides a faster response with a little less overhead on the server. Server.Transfer does not update the clients url history list or current url. Response.Redirect is used to redirect the user’s browser to another page or site. This perform as a trip back to the client where the client’s browser is redirected to the new page. The user’s browser history list is updated to reflect the new address.
Should user input data validation occur server-side or client-side? Why?
A: All user input data validation should occur on the server at a minimum. Additionally, client-side validation can be performed where deemed appropriate and feasable to provide a richer, more responsive experience for the user.
What type of code (server or client) is found in a Code-Behind class?
A: The answer is server-side code since code-behind is executed on the server. However, during the code-behind’s execution on the server, it can render client-side code such as JavaScript to be processed in the clients browser. But just to be clear, code-behind executes on the server, thus making it server-side code.
Suppose you want a certain ASP.NET function executed on MouseOver for a certain button. Where do you add an event handler?
A: Add an OnMouseOver attribute to the button. Example: btnSubmit.Attributes.Add(”onmouseover”,”someClientCodeHere();”);
What’s a bubbled event?
A: When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their event handlers, allowing the main DataGrid event handler to take care of its constituents.
When during the page processing cycle is ViewState available?
A: After the Init() and before the Page_Load(), or OnLoad() for a control.
What methods are fired during the page load?
A: Init() - when the page is instantiated
Load() - when the page is loaded into server memory
PreRender() - the brief moment before the page is displayed to the user as HTML
Unload() - when page finishes loading.
What’s the difference between Response.Write() and Response.Output.Write()?
A: Response.Output.Write() allows you to write formatted output.
Describe the role of inetinfo.exe, aspnet_isapi.dll and aspnet_wp.exe in the page loading process ?
A: inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things. When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request to the actual worker process aspnet_wp.exe.
A: It can contain many classes.
True or False: To test a Web service you must create a windows application or Web application to consume this service ?
A: False, the webservice comes with a test page and it provides HTTP-GET method to test.
Which control would you use if you needed to make sure the values in two different controls matched ?
A: CompareValidator Control
Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box ?
A: DataTextField property
What does WSDL stand for ?
A: (Web Services Description Language)
True or False: A Web service can only be written in .NET ?
A: False
What tag do you use to add a hyperlink column to the DataGrid ?
A:
What tags do you need to add within the asp:datagrid tags to bind columns manually ?
A: Set AutoGenerateColumns Property to false on the datagrid tag
What base class do all Web Forms inherit from ?
A: The Page class.
What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control ?
A: You must set the DataSource property and call the DataBind method
Which template must you provide, in order to display data in a Repeater control ?
A: ItemTemplate
If I’m developing an application that must accommodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing) what would be the best approach to maintain login-in state for the users ?
A: Maintain the login state security through a database.
What does the “EnableViewState” property do? Why would I want it on or off ?
A: It enables the viewstate on the page. It allows the page to save the users input on a form.
Suppose you want a certain ASP.NET function executed on MouseOver overa certain button. Where do you add an event handler ?
A: t’s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add(”onMouseOver”,”someClientCode();”)
What’s a bubbled event ?
A: When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.
What’s the difference between Codebehind=”MyCode.aspx.cs” andSrc=”MyCode.aspx.cs” ?
A: CodeBehind is relevant to Visual Studio.NET only.
Where do you store the information about the user’s locale ?
A: System.Web.UI.Page.Culture
Where does the Web page belong in the .NET Framework class hierarchy ?
A: System.Web.UI.Page
What’s the difference between Response.Write() andResponse.Output.Write() ?
A: The latter one allows you to write formattedoutput.
Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process ?
A: inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension),the ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker process aspnet_wp.exe.
What is method to get XML and schema from Dataset ?
getXML () and get Schema ()
Differences between dataset.clone and dataset.copy ?
A: Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data.
Copy - Copies both the structure and data for this DataSet.
How to check if a datareader is closed or opened ?
A: IsClosed()
In how many ways we can retrieve table records count? How to find the count of records in a dataset ?
A: foreach(DataTable thisTable in myDataSet.Tables){
// For each row, print the values of each column.
foreach(DataRow myRow in thisTable.Rows){
What happens when we issue Dataset.ReadXml command ?
A: Reads XML schema and data into the DataSet.
Explain different methods and Properties of DataReader which you have used in your project ?
A: Read
GetString
GetInt32
while (myReader.Read())
Console.WriteLine(”\t{0}\t{1}”, myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
Difference between DataReader and DataAdapter / DataSet and DataAdapter?
A: You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the DataReader can increase application performance and reduce system overhead because only one row at a time is ever in memory.
After creating an instance of the Command object, you create a DataReader by calling Command.ExecuteReader to retrieve rows from a data source, as shown in the following example.
SqlDataReader myReader = myCommand.ExecuteReader();
You use the Read method of the DataReader object to obtain a row from the results of the query.
while (myReader.Read())
Console.WriteLine(”\t{0}\t{1}”, myReader.GetInt32(0), myReader.GetString(1));
myReader.Close();
The DataSet is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source. It can be used with multiple and differing data sources, used with XML data, or used to manage data local to the application. The DataSet represents a complete set of data including related tables, constraints, and relationships among the tables. The methods and objects in a DataSet are consistent with those in the relational database model. The DataSet can also persist and reload its contents as XML and its schema as XML Schema definition language (XSD) schema.
The DataAdapter serves as a bridge between a DataSet and a data source for retrieving and saving data. The DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet to match the data in the data source, and Update, which changes the data in the data source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server database, you can increase overall performance by using the SqlDataAdapter along with its associated SqlCommand and SqlConnection. For other OLE DB-supported databases, use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.
What are the different namespaces used in the project to connect the database? What data providers available in .net to connect to database ?
A: • System.Data.OleDb – classes that make up the .NET Framework Data Provider for OLE DB-compatible data sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and read the results.
• System.Data.SqlClient – classes that make up the .NET Framework Data Provider for SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.
• System.Data.Odbc - classes that make up the .NET Framework Data Provider for ODBC. These classes allow you to access ODBC data source in the managed space.
• System.Data.OracleClient - classes that make up the .NET Framework Data Provider for Oracle. These classes allow you to access an Oracle data source in the managed space.
Difference between OLEDB Provider and SqlClient ?
A: SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The SqlClient data provider is fast. It’s faster than the Oracle provider, and faster than accessing database via the OleDb layer. It’s faster because it accesses the native library (which automatically gives you better performance), and it was written with lots of help from the SQL Server team.
What are relation objects in dataset and how & where to use them ?
A: In a DataSet that contains multiple DataTable objects, you can use DataRelation objects to relate one table to another, to navigate through the tables, and to return child or parent rows from a related table. Adding a DataRelation to a DataSet adds, by default, a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table.
The following code example creates a DataRelation using two DataTable objects in a DataSet. Each DataTable contains a column named CustID, which serves as a link between the two DataTable objects. The example adds a single DataRelation to the Relations collection of the DataSet. The first argument in the example specifies the name of the DataRelation being created. The second argument sets the parent DataColumn and the third argument sets the child DataColumn.
custDS.Relations.Add(”CustOrders”,
custDS.Tables[”Customers”].Columns[”CustID”],
custDS.Tables[”Orders”].Columns[”CustID”]);
OR
private void CreateRelation()
{
// Get the DataColumn objects from two DataTable objects in a DataSet.
DataColumn parentCol;
DataColumn childCol;
// Code to get the DataSet not shown here.
parentCol = DataSet1.Tables[”Customers”].Columns[”CustID”];
childCol = DataSet1.Tables[”Orders”].Columns[”CustID”];
// Create DataRelation.
DataRelation relCustOrder;
relCustOrder = new DataRelation(”CustomersOrders”, parentCol, childCol);
// Add the relation to the DataSet.
DataSet1.Relations.Add(relCustOrder);
}
How would u connect to database using .NET ?
A: SqlConnection nwindConn = new SqlConnection(”Data Source=localhost; Integrated Security=SSPI;” +
“Initial Catalog=northwind”);
nwindConn.Open();
Advantage of ADO.Net ?
A: o ADO.NET Does Not Depend On Continuously Live Connections
o Database Interactions Are Performed Using Data Commands
o Data Can Be Cached in Datasets
o Datasets Are Independent of Data Sources
o Data Is Persisted as XML
o Schemas Define Data Structures
What is the different between ASP.NET and VB.NET?
A: ASP.Net is an “environment”, and VB.Net is a programming language. You can write ASP.Net pages (called “Web Forms” by Microsoft) using VB.Net (or C#, or J# or Managed C++ or any one of a number of .Net compatible languages).
Confusingly, there is an IDE that Microsoft markets called VB.Net, which allows you to write and compile programs (WinForms, WebForms, class libraries etc) written in the language VB.Net
ASP.Net is simple a library that makes it easy for you to create web applications that run against the .NET runtime (similar to the java runtime).
VB.Net is a language that compiles against the common language runtime, like C#. Any .NET compliant language can use the asp.net libraries to create web applications.
Note : Actually there is not an IDE called VB.Net. Microsoft’s IDE is called Visual Studio.Net which can be used to manage VB.Net, C#, Eiffle, Fortran, and other languages.
How can we create custom controls in ASP.NET?
A: Custom Controls can be created in either of the following 3 methods.
1. Creating as a composite control : This method uses and combines the existing controls to give a custom functionality which can be used across different projects by adding to the control library. This can provide for event bubbling from child controls to the Parent container, custom event handling and properties. The CreateChildControls function of the Control class should be overridden for creating this custom control. This can also support design time rendering of the control.
2. Deriving from an existing control : This method of creating a custom control derives from an existing ASP .Net control and customizing the properties that we need. This also can support custom event handling, properties etc.,
3. Creating a control from Scratch : This method is the one which needs maximum programming. This method needs even the HTML code for the custom controls to be written by the programmer. This may also need one to implement the IPostBackDataHandler and IPostBackEventHandler interfaces. A detailed explanation with example for this is available at Rendering Custom Controls Sample in MSDN.
How many types of validation controls are provided by ASP.NET ?
A; RequiredField Validator Control,Range Validator Control, RegularExpression Validator Control,Custom Validator Control and Validation Summary Control are provided by ASP.NET.
Can you explain what is “AutoPostBack” feature in ASP.NET ?
A: AutoPostBack is built into the form-based server controls, and when enabled, automatically posts the page back to the server whenever the value of the control in question is changed.
How can you enable automatic paging in DataGrid ?
A: Using the Built-In Paging Controls
To use default paging, you set properties to enable paging, set the page size, and specify the style of the paging controls. Paging controls are LinkButton controls. You can choose from these types: Next and previous buttons. The button captions can be any text you want. Page numbers, which allow users to jump to a specific page. You can specify how many numbers are displayed; if there are more pages, an ellipsis ( … ) is displayed next to the numbers. You must also create an event-handling method that responds when users click a navigation control.
To use the built-in paging controlsSet the control’s AllowPaging property to true. Set the PageSize property to the number of items to display per page.
To set the appearance of the paging buttons, include a element into the page as a child of the DataGrid control. For syntax, see DataGrid Control Syntax. Create a handler for the grid’s PageIndexChanged event to respond to a paging request. The DataGridPageChangedEventsArgs enumeration contains the NewPageIndex property, which is the page the user would like to browse to. Set the grid’s CurrentPageIndex property to e.NewPageIndex, then rebind the data.
What is the difference between login controls and Forms authentication?
A: Login controls are an easy way to implement Forms authentication without having to write any code. For example, the Login control performs the same functions you would normally perform when using the FormsAuthentication class—prompt for user credentials, validate them, and issue the authentication ticket—but with all the functionality wrapped in a control that you can just drag from the Toolbox in Visual Studio. Under the covers, the login control uses the FormsAuthentication class (for example, to issue the authentication ticket) and ASP.NET membership (to validate the user credentials). Naturally, you can still use Forms authentication yourself, and applications you have that currently use it will continue to run.
What is Tracing in ASP.NET ?
A: ASP.NET introduces new functionality that allows you to write debug statements, directly in your code, without having to remove them from your application when it is deployed to production servers. Called tracing, this feature allows you to write variables or structures in a page, assert whether a condition is met, or simply trace through the execution path of your page or application.
How do we enable tracing ?
A; Instead of enabling tracing for individual pages, you can enable it for your entire application. In that case, every page in your application displays trace information. Application tracing is useful when you are developing an application because you can easily enable it and disable it without editing individual pages. When your application is complete, you can turn off tracing for all pages at once.When you enable tracing for an application, ASP.NET collects trace information for each request to the application, up to the maximum number of requests you specify. The default number of requests is 10. You can view trace information with the trace viewer.By default, when the trace viewer reaches its request limit, the application stops storing trace requests. However, you can configure application-level tracing to always store the most recent tracing data, discarding the oldest data when the maximum number of requests is reached.
To Enable Tracing for an application:
1.Open your Web site’s Web.config file. If no Web.config file exists, create a new file in the root folder and copy the following into it:
2.Add a trace element as a child of the system.web element.
3.In the trace element, set the enabled attribute to true.
4.If you want trace information to appear at the end of the page that it is associated with, set the trace element’s pageOutput attribute to true. If you want tracing information to be displayed only in the trace viewer, set the pageOutput attribute to false.For example, the following application trace configuration collects trace information for up to 40 requests and allows browsers on computers other than the server of origin to display the trace viewer. Trace information is not displayed in individual pages.
What exactly happens when ASPX page is requested from Browser?
A: At its core, the ASP.NET execution engine compiles the page into a class, which derives from the code behind class (which in turn derives directly or indirectly from the Page class). Then it injects the newly created class into the execution environment, instantiates it, and executes it. ASP.NET, on the other hand, can accept code in any language that is compatible with the .NET framework, because it’s compiled down natively just like other code.
How do you deploy an ASP.NET application?
You can deploy an ASP.NET Web application using any one of the following three deployment options.1.XCOPY Deployment
2.Using the Copy Project option in VS .NET
3.Deployment using VS.NET installer
ASP.NET Configuration.
A: ASP.NET Configuration
The ASP.NET configuration system features an extensible infrastructure that enables you to define configuration settings at the time your ASP.NET applications are first deployed so that you can add or revise configuration settings at any time with minimal impact on operational Web applications and servers.
The ASP.NET configuration system provides the following benefits:
* Configuration information is stored in XML-based text files. You can use any standard text editor or XML parser to create and edit ASP.NET configuration files.
* Multiple configuration files, all named Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies configuration settings to its own directory and all child directories below it. Configuration files in child directories can supply configuration information in addition to that inherited from parent directories, and the child directory configuration settings can override or modify settings defined in parent directories. The root configuration file named systemroot\Microsoft.NET\Framework\versionNumber\CONFIG\Machine.config provides ASP.NET configuration settings for the entire Web server.
* At run time, ASP.NET uses the configuration information provided by the Web.config files in a hierarchical virtual directory structure to compute a collection of configuration settings for each unique URL resource. The resulting configuration settings are then cached for all subsequent requests to a resource. Note that inheritance is defined by the incoming request path (the URL), not the file system paths to the resources on disk (the physical paths).
* ASP.NET detects changes to configuration files and automatically applies new configuration settings to Web resources affected by the changes. The server does not have to be rebooted for the changes to take effect. Hierarchical configuration settings are automatically recalculated and recached whenever a configuration file in the hierarchy is changed. The
section is an exception.
* The ASP.NET configuration system is extensible. You can define new configuration parameters and write configuration section handlers to process them.
* ASP.NET help protect configuration files from outside access by configuring Internet Information Services (IIS) to prevent direct browser access to configuration files. HTTP access error 403 (forbidden) is returned to any browser attempting to request a configuration file directly.
What can be stored in Web.config file?
A: There are number of important settings that can be stored in the configuration file. Here are some of the most frequently used configurations, stored conveniently inside Web.config file..
1. Database connections
2. Session States
3. Error Handling
4. Security
Difference between Web.config and machine.config?
A: web.config:
Web.config file, as it sounds like is a configuration file for the Asp .net web application. An Asp .net application has one web.config file which keeps the configurations required for the corresponding application. Web.config file is written in XML with specific tags having specific meanings.
machine.config
As web.config file is used to configure one asp .net web application, same way Machine.config file is used to configure the application according to a particular machine. That is, configuration done in machine.config file is affected on any application that runs on a particular machine. Usually, this file is not altered and only web.config is used which configuring applications
Where we can use DLL made in C#.Net ?
A: Supporting .Net, bcoz DLL made in C#.Net semicompiled version. Its not a com object. It is used only in .Net Framework.As it is to be compiled at runtime to byte code.
If A.equals(B) is true then A.getHashcode & B.getHashCode must always return same hash code.
A: The answer is False because it is given that A.equals(B) returns true i.e. objects are equal and now its hashCode is asked which is always independent of the fact that whether objects are equal or not. So, GetHashCode for both of the objects returns different value.
To Configure .Net for JIT activation what do you do?
A: Actually JIT activation is required for COM+ components which can be done by setting JustInTimeActivation attribute to true (choice A). For .net applications / components JIT comes in by default.
How do you import Activex component in to .NET?
A: An application called AXImp.exe shipped with .Net SDK is used.
This application does something similar as Tlbimp.exe does for non graphical COM components.
It creates a wrapper component that contains the type information that the .Net runtime can understand.
What is the use of fixed statement?
A: The fixed statement sets a pointer to a managed variable and “pins” that variable during the execution of statement.
Without fixed, pointers to managed variables would be of little use since garbage collection could relocate the variables unpredictably. (In fact, the C# compiler will not allow you to set a pointer to a managed variable except in a fixed statement.)
Eg:
Class A { public int i; }
A objA = new A; // A is a .net managed type
fixed(int *pt = &objA.i) // use fixed while using pointers with managed
// variables
{
*pt=45; // in this block use the pointer the way u want
}
What is the order of destructors called in a polymorphism hierarchy?
A: Destructors are called in reverse order of constructors. First destructor of most derived class is called followed by its parent’s destructor and so on till the topmost class in the hierarchy.
You don’t have control over when the first destructor will be called, since it is determined by the garbage collector. Sometime after the object goes out of scope GC calls the destructor, then its parent’s destructor and so on.
When a program terminates definitely all object’s destructors are called.
How can you sort the elements of the array in descending order?
A: int[] arr = new int[3];
arr[0] = 4;
arr[1] = 1;
arr[2] = 5;
Array.Sort(arr);
Array.Reverse(arr);
Is it possible to Override Private Virtual methods.
A: No, First of all you cannot declare a method as ‘private virtual’.
What does the volatile modifier do?
A: The system always reads the current value of a volatile object at the point it is requested, even if the previous instruction asked for a value from the same object. Also, the value of the object is written immediately on assignment.
The volatile modifier is usually used for a field that is accessed by multiple threads without using the lock statement to serialize access. Using the volatile modifier ensures that one thread retrieves the most up-to-date value written by another thread.
Is it possible to debug the classes written in other .Net languages in a C# project.?
A: It is definitely possible to debug other .Net languages code in a C# project. As everyone knows .net can combine code written in several .net languages into one single assembly. Same is true with debugging.
How do you debug an ASP.NET Web application?
A: Attach the aspnet_wp.exe process to the DbgClr debugger.
What debugging tools come with the .NET SDK?
A: 1. CorDBG – command-line debugger. To use CorDbg, you must compile the original C# file using the /debug switch.
2. DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR.
What is the difference between structures and enumeration?
A: Unlike classes, structs are value types and do not require heap allocation. A variable of a struct type directly contains the data of the struct, whereas a variable of a class type contains a reference to the data. They are derived from System.ValueType class.
Enum->An enum type is a distinct type that declares a set of named constants.They are strongly typed constants. They are unique types that allow to declare symbolic names to integral values. Enums are value types, which means they contain their own value, can’t inherit or be inherited from and assignment copies the value of one enum to another.
public enum Grade
{
A,
B,
C
}
What is Value type and refernce type in .Net?
A: Value Type : A variable of a value type always contains a value of that type. The assignment to a variable of a value type creates a copy of the assigned value, while the assignment to a variable of a reference type creates a copy of the reference but not of the referenced object.
The value types consist of two main categories:
* Stuct Type
* Enumeration Type
Reference Type :Variables of reference types, referred to as objects, store references to the actual data. This section introduces the following keywords used to declare reference types:
* Class
* Interface
* Delegate
This section also introduces the following built-in reference types:
* object
* string
What are the types of assemblies?
A: Static assemblies
These are the .NET PE files that you create at compile time.
Dynamic assemblies
These are PE-formatted, in-memory assemblies that you dynamically create at runtime using the classes in the System.Reflection.Emit namespace.
Private assemblies
These are static assemblies used by a specific application.
Public or shared assemblies These are static assemblies that must have a unique shared name and can be used by any application.
An application uses a private assembly by referring to the assembly using a static path or through an XML-based application configuration file. While the CLR doesn’t enforce versioning policies-checking whether the correct version is used-for private assemblies, it ensures that an application uses the correct shared assemblies with which the application was built. Thus, an application uses a specific shared assembly by referring to the specific shared assembly, and the CLR ensures that the correct version is loaded at runtime.
In .NET, an assembly is the smallest unit to which you can associate a version number
What is manifest?
A: It is the metadata that describes the assemblies.
What distributed process frameworks outside .NET do you know?
A: Distributed Computing Environment/Remote Procedure Calls (DEC/RPC), Microsoft Distributed Component Object Model (DCOM), Common Object Request Broker Architecture (CORBA), and Java Remote Method Invocation (RMI).
How do you retrieve the customized properties of a .NET application from XML .config file?
A: Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable.
When would you use ErrorProvider control?
A: ErrorProvider control is used in Windows Forms application. It is like Validation Control for ASP.NET pages. ErrorProvider control is used to provide validations in Windows forms and display user friendly messages to the user if the validation fails. E.g. if we went to validate the textBox1 should be empty, then we can validate as below
1). You need to place the errorprovide control on the form
private void textBox1_Validating(object sender,System.ComponentModel.CancelEventArgs e)
{
ValidateName();
}
private bool ValidateName()
{
bool bStatus = true;
if (textBox1.Text == "")
{
errorProvider1.SetError (textBox1,"Please enter your Name");
bStatus = false;
}
else
errorProvider1.SetError (textBox1,"");
return bStatus;
}
it check the textBox1 is empty . If it is empty, then a message Please enter your name is displayed.
What is the difference between Debug.Write and Trace.Write?
A: The Debug.Write call won’t be compiled when the DEBUGsymbol is not defined (when doing a release build). Trace.Write calls will be compiled. Debug.Write is for information you want only in debug builds, Trace.Write is for when you want it in release build as well.
What are different transaction options available for services components?
A: There are 5 transactions types that can be used with COM+. Whenever an object is registered with COM+ it has to abide either to these 5 transaction types.
Disabled: - There is no transaction. COM+ does not provide transaction support for this component.
Not Supported: - Component does not support transactions. Hence even if the calling component in the hierarchy is transaction enabled this component will not participate in the transaction.
Supported: - Components with transaction type supported will be a part of the transaction if the calling component has an active transaction.
If the calling component is not transaction enabled this component will not start a new transaction.
Required: - Components with this attribute require a transaction i.e. either the calling should have a transaction in place else this component will start a new transaction.
Required New: - Components enabled with this transaction type always require a new transaction. Components with required new transaction type instantiate a new transaction for themselves every time.
What does it meant to say “the canonical” form of XML?
A: The purpose of Canonical XML is to define a standard format for an XML document. Canonical XML is a very strict XML syntax, which lets documents in canonical XML be compared directly.
Using this strict syntax makes it easier to see whether two XML documents are the same. For example, a section of text in one document might read Black & White, whereas the same section of text might read Black & White in another document, and even in another. If you compare those three documents byte by byte, they’ll be different. But if you write them all in canonical XML, which specifies every aspect of the syntax you can use, these three documents would all have the same version of this text (which would be Black & White) and could be compared without problem. This Comparison is especially critical when xml documents are digitally signed. The digital signal may be interpreted in different way and the document may be rejected.
What are the mobile devices supported by .net platform?
A: The Microsoft .NET Compact Framework is designed to run on mobile devices such as mobile phones, Personal Digital Assistants (PDAs), and embedded devices. The easiest way to develop and test a Smart Device Application is to use an emulator.
These devices are divided into two main divisions:
1) Those that are directly supported by .NET (Pocket PCs, i-Mode phones, and WAP devices)
2) Those that are not (Palm OS and J2ME-powered devices).
What is a Windows Service and how does its lifecycle differ from a “standard” EXE?
A: Windows service is a application that runs in the background. It is equivalent to a NT service.
The executable created is not a Windows application, and hence you can’t just click and run it . it needs to be installed as a service, VB.Net has a facility where we can add an installer to our program and then use a utility to install the service. Where as this is not the case with standard exe
What is the difference between repeater over datalist and datagrid?
A: The Repeater class is not derived from the WebControl class, like the DataGrid and DataList. Therefore, the Repeater lacks the stylistic properties common to both the DataGrid and DataList. What this boils down to is that if you want to format the data displayed in the Repeater, you must do so in the HTML markup. The Repeater control provides the maximum amount of flexibility over the HTML produced. Whereas the DataGrid wraps the DataSource contents in an HTML < table >, and the DataList wraps the contents in either an HTML < table > or < span > tags (depending on the DataList’s RepeatLayout property), the Repeater adds absolutely no HTML content other than what you explicitly specify in the templates. While using Repeater control, If we wanted to display the employee names in a bold font we’d have to alter the “ItemTemplate” to include an HTML bold tag, Whereas with the DataGrid or DataList, we could have made the text appear in a bold font by setting the control’s ItemStyle-Font-Bold property to True. The Repeater’s lack of stylistic properties can drastically add to the development time metric. For example, imagine that you decide to use the Repeater to display data that needs to be bold, centered, and displayed in a particular font-face with a particular background color. While all this can be specified using a few HTML tags, these tags will quickly clutter the Repeater’s templates. Such clutter makes it much harder to change the look at a later date. Along with its increased development time, the Repeater also lacks any built-in functionality to assist in supporting paging, editing, or editing of data. Due to this lack of feature-support, the Repeater scores poorly on the usability scale.
However, The Repeater’s performance is slightly better than that of the DataList’s, and is more noticeably better than that of the DataGrid’s. Following figure shows the number of requests per second the Repeater could handle versus the DataGrid and DataList
What is a PostBack?
A: The process in which a Web page sends data back to the same page on the server.
Is it possible to prevent a browser from caching an ASPX page?
A: Just call SetNoStore on the HttpCachePolicy object exposed through the Response object’s Cache property, as demonstrated here:
SetNoStore works by returning a Cache-Control: private, no-store header in the HTTP response. In this example, it prevents caching of a Web page that shows the current time.
What are VSDISCO files?
A: VSDISCO files are DISCO files that support dynamic discovery of Web services. If you place the following VSDISCO file in a directory on your Web server, for example, it returns references to all ASMX and DISCO files in the host directory and any subdirectories not noted in elements:
Name two properties common in every validation control?
A: ControlToValidate property and Text property.
What namespace does the Web page belong in the .NET Framework class hierarchy?
A: System.Web.UI.Page
Are the actual permissions for the application defined at run-time or compile-time?
A: The CLR computes actual permissions at runtime based on code group membership and the calling chain of the code.
What is the difference between authentication and authorization?
A: Authentication happens first. You verify user’s identity based on credentials. Authorization is making sure the user only gets access to the resources he has credentials for.
What is a code group?
A: A code group is a set of assemblies that share a security context.
How can C# app request minimum permissions?
A: Using System.Security.Permissions;
[assembly:FileDialogPermissionAttribute(SecurityAction.RequestMinimum, Unrestricted=true)].
How can you work with permissions from your .NET application?
A: You can request permission to do something and you can demand certain permissions from other apps. You can also refuse permissions so that your app is not inadvertently used to destroy some data.
What’s the difference between code-based security and role-based security? Which one is better?
A: Code security is the approach of using permissions and permission sets for a given code to run. The admin, for example, can disable running executables off the Internet or restrict access to corporate database to only few applications. Role-based security most of the time involves the code running with the privileges of the current user. This way the code cannot supposedly do more harm than mess up a single user account. There’s no better, or 100% thumbs-up approach, depending on the nature of deployment, both code-based and role-based security could be implemented to an extent.
How do you display an editable drop-down list?
A: Displaying a drop-down list requires a template column in the grid. Typically, the ItemTemplate contains a control such as a data-bound Label control to show the current value of a field in the record. You then add a drop-down list to the EditItemTemplate. In Visual Studio, you can add a template column in the Property builder for the grid, and then use standard template editing to remove the default TextBox control from the EditItemTemplate and drag a DropDownList control into it instead. Alternatively, you can add the template column in HTML view. After you have created the template column with the drop-down list in it, there are two tasks. The first is to populate the list. The second is to preselect the appropriate item in the list — for example, if a book’s genre is set to “fiction,” when the drop-down list displays, you often want “fiction” to be preselected.
How to manage pagination in a page?
A: Using pagination option in DataGrid control. We have to set the number of records for a page, then it takes care of pagination by itself.
Can the validation be done in the server side?
A: Client side validation is done by default. Server side validation is also possible. We can switch off the client side and server side can be done.
How do you validate the controls in an ASP .NET page?
A: We can Validate the controls in an ASP.NET page by using special validation controls that are meant for this. We have Range Validator, Email Validator.
What is smart navigation?
A: The cursor position is maintained when the page gets refreshed due to the server side validation and the page gets refreshed.
How is .NET able to support multiple languages?
A: A language should comply with the Common Language Runtime standard to become a .NET language. In .NET, code is compiled to Microsoft Intermediate Language (MSIL for short). This is called as Managed Code. This Managed code is run in .NET environment. So after compilation to this IL the language is not a barrier. A code can call or use a function written in another language.
What is the difference between Java and .NET garbage collectors?
A: Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you’re using. Microsoft standardized on their garbage collection.
What is the CLI? Is it the same as the CLR?
A: The CLI (Common Language Infrastructure) is the definiton of the fundamentals of the .NET framework - the Common Type System (CTS), metadata, the Virtual Execution Environment (VES) and its use of intermediate language (IL), and the support of multiple programming languages via the Common Language Specification (CLS). The CLI is documented through ECMA
The CLR (Common Language Runtime) is Microsoft’s primary implementation of the CLI. Microsoft also have a shared source implementation known as ROTOR, for educational purposes, as well as the .NET Compact Framework for mobile devices. Non-Microsoft CLI implementations include Mono and DotGNU Portable.NET.
What is an application domain?
A: An AppDomain can be thought of as a lightweight process. Multiple AppDomains can exist inside a Win32 process. The primary purpose of the AppDomain is to isolate applications from each other, and so it is particularly useful in hosting scenarios such as ASP.NET. An AppDomain can be destroyed by the host without affecting other AppDomains in the process.
Win32 processes provide isolation by having distinct memory address spaces. This is effective, but expensive. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other’s memory.
One non-obvious use of AppDomains is for unloading types. Currently the only way to unload a .NET type is to destroy the AppDomain it is loaded into. This is particularly useful if you create and destroy types on-the-fly via reflection
Does .NET support one-way Web service operations? Does Microsoft SOAP Toolkit support one-way Web service operations?
A: Yes, .NET framework does support one-way messages. To set a void method as one-way operation, set the OneWay property to true on SoapDocumentMethodAttribute or on SoapRpcMethodAttribute attribute. In such cases, the Web service client is intending to just send some notification to the server and not expect any response. The server in such cases returns 202 Accepted HTTP response to the client. And there will be no output message in the WSDL file for such methods. The support for one-way Web service operations was also added in the latest SOAP Toolkit 3.0 release.
Does .NET support validating XML documents against DTDs?
A: Yes, in addition to XDR and XSD schema validation, .NET continues to support the DTD to validate the XML documents. The System.Xml namespace contains a class named XmlValidatingReader that can be used to validate the XML documents.
What is an .ASP file?
A: It is a Text File that contains the combination of the following:
• Text
• HTML tags
• Script Commands
Where would you use an iHTTPModule, and what are the limitations of anyapproach you might take in implementing one?
A: One of ASP.NET’s most useful features is the extensibility of the HTTP pipeline, the path that data takes between client and server. You can use them to extend your ASP.NET applications by adding pre- and post-processing to each HTTP request coming into your application. For example, if you wanted custom authentication facilities for your application, the best technique would be to intercept the request when it comes in and process the request in a custom HTTP module.
Can you configure a .NET Remoting object via XML file?
A: Yes, via machine.config and application level .config file (or web.config in ASP.NET). Application-level XML settings take precedence over machine.config.
How do I change the permission set for a code group?
A: Use caspol. If you are the machine administrator, you can operate at the ‘machine’ level - which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive.
For example, to allow intranet code to do what it likes you might do this: caspol -cg 1.2 FullTrust
Note that because this is more permissive than the default policy (on a standard system), you should only do this at the machine level - doing it at the user level will have no effect.
How to set the debug mode?
A: Debug Mode for ASP.NET applications - To set ASP.NET appplication in debugging mode, edit the application’s web.config and assign the “debug” attribute in < compilation > section to “true” as show below:
< configuration >
< system.web >
< compilation defaultLanguage="vb" debug="true" / >
….
…
..
< / configuration >
This case-sensitive attribute ‘debug tells ASP.NET to generate symbols for dynamically generated files and enables the
debugger to attach to the ASP.NET application. ASP.NET will detect this change automatically, without the need to restart the server. Debug Mode for ASP.NET Webservices - Debugging an XML Web service created with ASP.NET is similar to the debugging an ASP.NET Web application.
What platforms does the .NET Framework run on?
A: The runtime supports Windows XP, Windows 2000, NT4 SP6a and Windows ME/98. Windows 95 is not supported. Some parts of the framework do not work on all platforms - for example, ASP.NET is only supported on Windows XP and Windows 2000. Windows 98/ME cannot be used for development. IIS is not supported on Windows XP Home Edition, and so cannot be used to host ASP.NET. However, the ASP.NET Web Matrix web server does run on XP Home. The Mono project is attempting to implement the .NET framework on Linux.
How do you handle data concurrency in .NET ?
A: One of the key features of the ADO.NET DataSet is that it can be a self-contained and disconnected data store. It can contain the schema and data from several rowsets in DataTable objects as well as information about how to relate the DataTable objects-all in memory. The DataSet neither knows nor cares where the data came from, nor does it need a link to an underlying data source. Because it is data source agnostic you can pass the DataSet around networks or even serialize it to XML and pass it across the Internet without losing any of its features. However, in a disconnected model, concurrency obviously becomes a much bigger problem than it is in a connected model.
In this column, I’ll explore how ADO.NET is equipped to detect and handle concurrency violations. I’ll begin by discussing scenarios in which concurrency violations can occur using the ADO.NET disconnected model. Then I will walk through an ASP.NET application that handles concurrency violations by giving the user the choice to overwrite the changes or to refresh the out-of-sync data and begin editing again. Because part of managing an optimistic concurrency model can involve keeping a timestamp (rowversion) or another type of flag that indicates when a row was last updated, I will show how to implement this type of flag and how to maintain its value after each database update.
What is WSDL?
A: WSDL is the Web Service Description Language, and it is implemented as a specific XML vocabulary. While it’s very much more complex than what can be described here, there are two important aspects to WSDL with which you should be aware. First, WSDL provides instructions to consumers of Web Services to describe the layout and contents of the SOAP packets the Web Service intends to issue. It’s an interface description document, of sorts. And second, it isn’t intended that you read and interpret the WSDL. Rather, WSDL should be processed by machine, typically to generate proxy source code (.NET) or create dynamic proxies on the fly (the SOAP Toolkit or Web Service Behavior).
What does AspCompat=”true” mean and when should I use it?
A: AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects–that is, COM objects registered ThreadingModel=Apartment. That includes all COM objects written with Visual Basic 6.0. AspCompat should also be set to true (regardless of threading model) if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true:
Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available to the COM components by placing unmanaged wrappers around the equivalent ASP.NET objects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the request for the page) and the COM objects it creates share an apartment. AspCompat=”true” forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel=Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat=”true,” request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it’s marshaled across apartment boundaries.
Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don’t access ASP intrinsic objects and that are registered ThreadingModel=Free or ThreadingModel=Both.
What is Web Gardening? How would using it affect a design?
A: The Web Garden Model: The Web garden model is configurable through the section of the machine.config file. Notice that the section is the only configuration section that cannot be placed in an application-specific web.config file. This means that the Web garden mode applies to all applications running on the machine. However, by using the node in the machine.config source, you can adapt machine-wide settings on a per-application basis.
Two attributes in the section affect the Web garden model. They are webGarden and cpuMask. The webGarden attribute takes a Boolean value that indicates whether or not multiple worker processes (one per each affinitized CPU) have to be used. The attribute is set to false by default. The cpuMask attribute stores a DWORD value whose binary representation provides a bit mask for the CPUs that are eligible to run the ASP.NET worker process. The default value is -1 (0xFFFFFF), which means that all available CPUs can be used. The contents of the cpuMask attribute is ignored when the webGarden attribute is false. The cpuMask attribute also sets an upper bound to the number of copies of aspnet_wp.exe that are running.
Web gardening enables multiple worker processes to run at the same time. However, you should note that all processes will have their own copy of application state, in-process session state, ASP.NET cache, static data, and all that is needed to run applications. When the Web garden mode is enabled, the ASP.NET ISAPI launches as many worker processes as there are CPUs, each a full clone of the next (and each affinitized with the corresponding CPU). To balance the workload, incoming requests are partitioned among running processes in a round-robin manner. Worker processes get recycled as in the single processor case. Note that ASP.NET inherits any CPU usage restriction from the operating system and doesn’t include any custom semantics for doing this.
All in all, the Web garden model is not necessarily a big win for all applications. The more stateful applications are, the more they risk to pay in terms of real performance. Working data is stored in blocks of shared memory so that any changes entered by a process are immediately visible to others. However, for the time it takes to service a request, working data is copied in the context of the process. Each worker process, therefore, will handle its own copy of working data, and the more stateful the application, the higher the cost in performance. In this context, careful and savvy application benchmarking is an absolute must.
Changes made to the section of the configuration file are effective only after IIS is restarted. In IIS 6, Web gardening parameters are stored in the IIS metabase; the webGarden and cpuMask attributes are ignored.
Can we handle the error and redirect to some pages using web.config?
A: Yes, we can do this, but to handle errors, we must know the error codes; only then we can take the user to a proper error message page, else it may confuse the user.
CustomErrors Configuration section in web.config file:
The default configuration is:
< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" >
< error statusCode="404" redirect="Notfound.aspx" / >
< /customErrors >
If mode is set to Off, custom error messages will be disabled. Users will receive detailed exception error messages.
If mode is set to On, custom error messages will be enabled.
If mode is set to RemoteOnly, then users will receive custom errors, but users accessing the site locally will receive detailed error messages.
Add an < error > tag for each error you want to handle. The error tag will redirect the user to the Notfound.aspx page when the site returns the 404 (Page not found) error.
[Example]
There is a page MainForm.aspx
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
‘Put user code to initialize the page here
Dim str As System.Text.StringBuilder
str.Append(”hi”) ‘ Error Line as str is not instantiated
Response.Write(str.ToString)
End Sub
[Web.Config]
< customErrors mode="On" defaultRedirect="Error.aspx"/ >
‘ a simple redirect will take the user to Error.aspx [user defined] error file.
< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" >
< error statusCode="404" redirect="Notfound.aspx" / >
< /customErrors >
‘This will take the user to NotFound.aspx defined in IIS.
What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?
A: ViewState is the mechanism ASP.NET uses to keep track of server control state values that don’t otherwise post back as part of the HTTP form. ViewState Maintains the UI State of a Page
ViewState is base64-encoded. It is not encrypted but it can be encrypted by setting EnableViewStatMAC=”true” & setting the machineKey validation type to 3DES. If you want to NOT maintain the ViewState, include the directive < %@ Page EnableViewState="false" % > at the top of an .aspx page or add the attribute EnableViewState=”false” to any control.
When you’re running a component within ASP.NET, what process is it running within on Windows XP? Windows 2000? Windows 2003?
A: On Windows 2003 (IIS 6.0) running in native mode, the component is running within the w3wp.exe process associated with the application pool which has been configured for the web application containing the component.
On Windows 2003 in IIS 5.0 emulation mode, 2000, or XP, it’s running within the IIS helper process whose name I do not remember, it being quite a while since I last used IIS 5.0.
Difference between asp and asp.net?.
A: “ASP (Active Server Pages) and ASP.NET are both server side technologies for building web sites and web applications, ASP.NET is Managed compiled code - asp is interpreted. and ASP.net is fully Object oriented. ASP.NET has been entirely re-architected to provide a highly productive programming experience based on the .NET Framework, and a robust infrastructure for building reliable and scalable web
applications.”
What is advantage of viewstate and what are benefits?
A: When a form is submitted in classic ASP, all form values are cleared. Suppose you have submitted a form with a lot of information and the server comes back with an error. You will have to go back to the form and correct the information. You click the back button, and what happens…….ALL form values are CLEARED, and you will have to start all over again! The site did not maintain your ViewState.With ASP .NET, the form reappears in the browser window together with all form values.This is because ASP .NET maintains your ViewState. The ViewState indicates the status of the page when submitted to the server.
What is an HTML “entity”?
A: An entity is a specific character string that has the effect of causing a formatting program to select and present a particular character or notation.
Difference between Anchor and Dock Properties?
A: Dock Property->Gets or sets which edge of the parent container a control is docked to. A control can be docked to one edge of its parent container or can be docked to all edges and fill the parent container. For example, if you set this property to DockStyle.Left, the left edge of thecontrol will be docked to the left edge of its parent control. Additionally, the docked edge of the control is resized to match that of its container
control.
Anchor Property->Gets or sets which edges of the control are anchored to the edges of its container. A control can be anchored to one or more edges of its parent container. Anchoring a control to its parent ensures that the anchored edges remain in the same position relative to the edges of the parent container when the parent container is resized.
What’s the safest way to deploy a Windows Forms app?
A: Web deployment: the user always downloads the latest version of the code, the program runs within security sandbox, properly written app will not require additional security privileges.
What class does Icon derive from?
A: Isn’t it just a Bitmap with a wrapper name around it? No, Icon lives in System.Drawing namespace. It’s not a Bitmap by default, and is treated separately by .NET. However, you can use ToBitmap method to get a valid Bitmap object from a valid Icon object.
When displaying fonts, what’s the difference between pixels, points and ems?
A: A pixel is the lowest-resolution dot the computer monitor supports. Its size depends on user’s settings and monitor size. A point is always 1/72 of an inch. An em is the number of pixels that it takes to display the letter M.
Where on the Internet would you look for Web services?
A: UDDI repositaries like uddi.microsoft.com, IBM UDDI node, UDDI Registries in Google Directory, enthusiast sites like XMethods.net.
What is the transport protocol you use to call a Web service?
A: SOAP. Transport Protocols: It is essential for the acceptance of Web Services that they are based on established Internet infrastructure. This in fact imposes the usage of of the HTTP, SMTP and FTP protocols based on the TCP/IP family of transports. Messaging Protocol: The format of messages exchanged between Web Services clients and Web Services should be vendor neutral and should not carry details about the technology used to implement the service. Also, the message format should allow for extensions and different bindings to specific transport protocols. SOAP and ebXML Transport are specifications which fulfill these requirements. We expect that the W3C XML Protocol Working Group defines a successor standard.
How do you turn off cookies for one page in your site?
A: Use the Cookie.Discard Property which Gets or sets the discard flag set by the server. When true, thisproperty instructs the client application not to save the Cookie on the user’s hard disk when a session ends.
Whats an assembly?
A: Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly.
What are CAO’s i.e. Client Activated Objects ?
A: Client-activated objects are objects whose lifetimes are controlled by the calling application domain, just as they would be if the object were local to the client. With client activation, a round trip to the server occurs when the client tries to create an instance of the server object, and the client proxy is created using an object reference (ObjRef) obtained on return from the creation of the remote object on the server. Each time a client creates an instance of a client-activated type, that instance will service only that particular reference in that particular client until its lease expires and its memory is recycled. If a calling application domain creates two new instances of the remote type, each of the client references will invoke only the particular instance in the server application domain from which the reference was returned.
In COM, clients hold an object in memory by holding a reference to it. When the last client releases its last reference, the object can delete itself. Client activation provides the same client control over the server object’s lifetime, but without the complexity of maintaining references or the constant pinging to confirm the continued existence of the server or client. Instead, client-activated objects use lifetime leases to determine how long they should continue to exist. When a client creates a remote object, it can specify a default length of time that the object should exist. If the remote object reaches its default lifetime limit, it contacts the client to ask whether it should continue to exist, and if so, for how much longer. If the client is not currently available, a default time is also specified for how long the server object should wait while trying to contact the client before marking itself for garbage collection. The client might even request an indefinite default lifetime, effectively preventing the remote object from ever being recycled until the server application domain is torn down. The difference between this and a server-activated indefinite lifetime is that an indefinite server-activated object will serve all client requests for that type, whereas the client-activated instances serve only the client and the reference that was responsible for their creation. For more information, see Lifetime Leases.
To create an instance of a client-activated type, clients either configure their application programmatically (or using a configuration file) and call new (New in Visual Basic), or they pass the remote object’s configuration in a call to Activator.CreateInstance. The following code example shows such a call, assuming a TcpChannel has been registered to listen on port 8080.
What is Com Callable wrapper?when it will created?
A: .NET components are accessed from COM via a COM Callable Wrapper (CCW). This is similar to a RCW, but works in the opposite direction. Again, if the wrapper cannot be automatically generated by the .NET development tools, or if the automatic behaviour is not desirable, a custom CCW can be developed. Also, for COM to ’see’ the .NET component, the .NET component must be registered in the registry.CCWs also manage the object identity and object lifetime of the managed objects they wrap.
What is Runtime Callable wrapper?.when it will created?.
A: The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW). Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a .NET client and a COM object. This wrapper turns the COM interfaces exposed by the COM component into .NET-compatible interfaces. For oleautomation (attribute indicates that an interface is compatible with Automation) interfaces, the RCW can be generated automatically from a type library. For non-oleautomation interfaces, it may be necessary to develop a custom RCW which manually maps the types exposed by the COM interface to .NET-compatible types.
What’s the difference between WindowsDefaultLocation and WindowsDefaultBounds?
A: WindowsDefaultLocation tells the form to start up at a location selected by OS, but with internally specified size. WindowsDefaultBounds delegates both size and starting position choices to the OS.
What’s the safest way to deploy a Windows Forms app?
A: Web deployment: the user always downloads the latest version of the code, the program runs within security sandbox, properly written app will not require additional security privileges.
What’s a proxy of the server object in .NET Remoting?
A; It’s a fake copy of the server object that resides on the client side and behaves as if it was the server. It handles the communication between real server object and the client object. This process is also known as marshaling.
When would you use .NET Remoting and when Web services?
A: Use remoting for more efficient exchange of information when you control both ends of the application. Use Web services for open-protocol-based information exchange when you are just a client or a server with the other end belonging to someone else.
What are channels in .NET Remoting?
A: Channels represent the objects that transfer the other serialized objects from one application domain to another and from one computer to another, as well as one process to another on the same box. A channel must exist before an object can be transferred.
What security measures exist for .NET Remoting in System.Runtime.Remoting?
A: Security should be taken care of at the application level. Cryptography and other security techniques can be applied at application or server level.
What technology enables out-of-proc communication in .NET?
A: Most usually Remoting;.NET remoting enables client applications to use objects in other processes on the same computer or on any other computer available on its network.While you could implement an out-of-proc component in any number of other ways, someone using the term almost always means Remoting.
What is ADO .NET and what is difference between ADO and ADO.NET?
A: ADO.NET is stateless mechanism. I can treat the ADO.Net as a separate in-memory database where in I can use relationships between the tables and select insert and updates to the database. I can update the actual database as a batch.
Can you declare a C++ type destructor in C# like ~MyClass()?
A: Yes, but what’s the point, since it will call Finalize(), and Finalize() has no guarantees when the memory will be cleaned up, plus, it introduces additional load on the garbage collector.
Contrast DTDs versus XSDs. What are their similarities and differences? Which is preferred and why?
A: Document Type Definition (DTD) describes a model or set of rules for an XML document. XML Schema Definition (XSD) also describes the structure of an XML document but XSDs are much more powerful. The disadvantage with the Document Type Definition is it doesn’t support data types beyond the basic 10 primitive types. It cannot properly define the type of data contained by the tag. An Xml Schema provides an Object Oriented approach to defining the format of an xml document. The Xml schema support most basic programming types like integer, byte, string, float etc., We can also define complex types of our own which can be used to define a xml document. Xml Schemas are always preferred over DTDs as a document can be more precisely defined using the XML Schemas because of its rich support for data representation.
Why is the XML InfoSet specification different from the Xml DOM? What does the InfoSet attempt to solve?
A: “The XML Information Set (Infoset) defines a data model for XML. The Infoset describes the abstract representation of an XML Document. Infoset is the generalized representation of the XML Document, which is primarily meant to act as a set of definitions used by XML technologies to formally describe what parts of an XML document they operate upon.
The Document Object Model (DOM) is one technology for representing an XML Document in memory and to programmatically read, modify and manipulate a xml document. Infoset helps defining generalized standards on how to use XML that is not dependent or tied to a particular XML specification or API. The Infoset tells us what part of XML Document should be considered as significant information.
How does VB.NET/C# achieve polymorphism?
A: Polymorphism is also achieved through interfaces. Like abstract classes, interfaces also describe the methods that a class needs to implement. The difference between abstract classes and interfaces is that abstract classes always act as a base class of the related classes in the class hierarchy. For example, consider a hierarchy-car and truck classes derived from four-wheeler class; the classes two-wheeler and four-wheeler derived from an abstract class vehicle. So, the class ‘vehicle’ is the base class in the class hierarchy. On the other hand dissimilar classes can implement one interface. For example, there is an interface that compares two objects. This interface can be implemented by the classes like box, person and string, which are unrelated to each other.
C# allows multiple interface inheritance. It means that a class can implement more than one interface. The methods declared in an interface are implicitly abstract. If a class implements an interface, it becomes mandatory for the class to override all the methods declared in the interface, otherwise the derived class would become abstract.
Can you explain what inheritance is and an example of when you might use it? The savingaccount class has two data members-accno that stores account number, and trans that keeps track of the number of transactions. We can create an object of savingaccount class as shown below.
savingaccount s = new savingaccount ( “Amar”, 5600.00f ) ;
From the constructor of savingaccount class we have called the two-argument constructor of the account class using the base keyword and passed the name and balance to this constructor using which the data member’s name and balance are initialised.
We can write our own definition of a method that already exists in a base class. This is called method overriding. We have overridden the deposit( ) and withdraw( ) methods in the savingaccount class so that we can make sure that each account maintains a minimum balance of Rs. 500 and the total number of transactions do not exceed 10. From these methods we have called the base class’s methods to update the balance using the base keyword. We have also overridden the display( ) method to display additional information, i.e. account number.
Working of currentaccount class is more or less similar to that of savingaccount class. Using the derived class’s object, if we call a method that is not overridden in the derived class, the base class method gets executed. Using derived class’s object we can call base class’s methods, but the reverse is not allowed.
Unlike C++, C# does not support multiple inheritance. So, in C# every class has exactly one base class. Now, suppose we declare reference to the base class and store in it the address of instance of derived class as shown below.
account a1 = new savingaccount ( “Amar”, 5600.00f ) ;
account a2 = new currentaccount ( “MyCompany Pvt. Ltd.”, 126000.00f) ;
Such a situation arises when we have to decide at run-time a method of which class in a class hierarchy should get called. Using a1 and a2, suppose we call the method display( ), ideally the method of derived class should get called. But it is the method of base class that gets called. This is because the compiler considers the type of reference (account in this case) and resolves the method call. So, to call the proper method we must make a small change in our program. We must use the virtual keyword while defining the methods in base class as shown below.
public virtual void display( ) { }
We must declare the methods as virtual if they are going to be overridden in derived class. To override a virtual method in derived classes we must use the override keyword as given below.
public override void display( ) { }
Now it is ensured that when we call the methods using upcasted reference, it is the derived class’s method that would get called. Actually, when we declare a virtual method, while calling it, the compiler considers the contents of the reference rather than its type.
If we don’t want to override base class’s virtual method, we can declare it with new modifier in derived class. The new modifier indicates that the method is new to this class and is not an override of a base class method.
What is Jit compilers?.how many are available in clr?
A: Just-In-Time compiler- it converts the language that you write in .Net into machine language that a computer can understand. there are tqo types of JITs one is memory optimized & other is performace optimized.
What is MSIL?
A: When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Before code can be run, MSIL must be converted to CPU-specific code, usually by a just-in-time (JIT) compiler. Because the common language runtime supplies one or more JIT compilers for each computer architecture it supports, the same set of MSIL can be JIT-compiled and run on any supported architecture.
When a compiler produces MSIL, it also produces metadata. Metadata describes the types in your code, including the definition of each type, the signatures of each type’s members, the members that your code references, and other data that the runtime uses at execution time. The MSIL and metadata are contained in a portable executable (PE) file that is based on and extends the published Microsoft PE and common object file format (COFF) used historically for executable content. This file format, which accommodates MSIL or native code as well as metadata, enables the operating system to recognize common language runtime images. The presence of metadata in the file along with the MSIL enables your code to describe itself, which means that there is no need for type libraries or Interface Definition Language (IDL). The runtime locates and extracts the metadata from the file as needed during execution.
What is global assembly cache?
A: Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer. There are several ways to deploy an assembly into the global assembly cache:
• Use an installer designed to work with the global assembly cache. This is the preferred option for installing assemblies into the global assembly cache. Use a developer tool called the Global Assembly Cache tool (Gacutil.exe), provided by the .NET Framework SDK.
• Use Windows Explorer to drag assemblies into the cache.
What is namespaces?.
A: Namespace is a logical naming scheme for group related types.Some class types that logically belong together they can be put into a common namespace. They prevent namespace collisions and they provide scoping. They are imported as “using” in C# or “Imports” in Visual Basic. It seems as if these directives specify a particular assembly, but they don’t. A namespace can span multiple assemblies, and an assembly can define multiple namespaces. When the compiler needs the definition for a class type, it tracks through each of the different imported namespaces to the type name and searches each referenced assembly until it is found.
Namespaces can be nested. This is very similar to packages in Java as far as scoping is concerned.
What are delegates?where are they used ?
A: A delegate defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure.
What is a formatter?
A; A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing and decoding messages into data on the other end.
Are private class-level variables inherited?
A: Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
Different b/w .NET & J2EE ?
A: Differences between J2EE and the .NET Platform
Vendor Neutrality
The .NET platform is not vendor neutral, it is tied to the Microsoft operating systems. But neither are any of the J2EE implementations
Many companies buy into J2EE believing that it will give them vendor neutrality. And, in fact, this is a stated goal of Sun’s vision:
A wide variety of J2EE product configurations and implementations, all of which meet the requirements of this specification, are possible. A portable J2EE application will function correctly when successfully deployed in any of these products. (ref : Java 2 Platform Enterprise Edition Specification, v1.3, page 2-7 available at http://java.sun.com/j2ee/)
Overall Maturity
Given that the .NET platform has a three year lead over J2EE, it should be no surprise to learn that the .NET platform is far more mature than the J2EE platform. Whereas we have high volume highly reliable web sites using .NET technologies (NASDAQ and Dell being among many examples)
Interoperability and Web Services
The .NET platform eCollaboration model is, as I have discussed at length, based on the UDDI and SOAP standards. These standards are widely supported by more than 100 companies. Microsoft, along with IBM and Ariba, are the leaders in this area. Sun is a member of the UDDI consortium and recognizes the importance of the UDDI standards.
In a recent press release, Sun’s George Paolini, Vice President for the Java Community
Development, says:”Sun has always worked to help establish and support open, standards-based technologies that facilitate the growth of network-based applications, and we see UDDI as an important project to establish a registry framework for business-to-business e-commerce
But while Sun publicly says it believes in the UDDI standards, in reality, Sun has done nothing whatsoever to incorporate any of the UDDI standards into J2EE.
Framework Support
The .NET platform includes such an eCommerce framework called Commerce Server. At this point, there is no equivalent vendor-neutral framework in the J2EE space. With J2EE, you should assume that you will be building your new eCommerce solution from scratch
Moreover, no matter what [J2EE] vendor you choose, if you expect a component framework that will allow you to quickly field complete e-business applications, you are in for a frustrating experience
Language
In the language arena, the choice is about as simple as it gets. J2EE supports Java, and only Java. It will not support any other language in the foreseeable future. The .NET platform supports every language except Java (although it does support a language that is syntactically and functionally equivalent to Java, C#). In fact, given the importance of the .NET platform as a language independent vehicle, it is likely that any language that comes out in the near future will include support for the .NET platform.
Some companies are under the impression that J2EE supports other languages. Although both IBM’s WebSphere and BEA’s WebLogic support other languages, neither does it through their J2EE technology. There are only two official ways in the J2EE platform to access other languages, one through the Java Native Interface and the other through CORBA interoperability. Sun recommends the later approach. As Sun’s Distinguished Scientist and Java Architect Rick Cattell said in a recent interview.
Portability
The reason that operating system portability is a possibility with J2EE is not so much because of any inherent portability of J2EE, as it is that most of the J2EE vendors support multiple operating systems. Therefore as long as one sticks with a given J2EE vendor and a given database vendor, moving from one operating system to another should be possible. This is probably the single most important benefit in favor of J2EE over the .NET platform, which is limited to the Windows operating system. It is worth noting, however, that Microsoft has submitted the specifications for C# and a subset of the .NET Framework (called the common language infrastructure) to ECMA, the group that standardizes JavaScript.
J2EE offers an acceptable solution to ISVs when the product must be marketed to non-Windows customers, particularly when the J2EE platform itself can be bundled with the ISV’s product as an integrated offering.
If the primary customer base for the ISV is Windows customers, then the .NET platform should be chosen. It will provide much better performance at a much lower cost.
Client device independence
The major difference being that with Java, it is the presentation tier programmer that determines the ultimate HTML that will be delivered to the client, and with .NET, it is a Visual Studio.NET control.
This Java approach has three problems. First, it requires a lot of code on the presentation tier, since every possible thin client system requires a different code path. Second, it is very difficult to test the code with every possible thin client system. Third, it is very difficult to add new thin clients to an existing application, since to do so involves searching through, and modifying a tremendous amount of presentation tier logic.
The .NET Framework approach is to write device independent code that interacts with visual controls. It is the control, not the programmer, that is responsible for determining what HTML to deliver, based on the capabilities of the client device.. In the .NET Framework model, one can forget that such a thing as HTML even exists!
Conclusion
Sun’s J2EE vision is based on a family of specifications that can be implemented by many vendors. It is open in the sense that any company can license and implement the technology, but closed in the sense that it is controlled by a single vendor, and a self contained architectural island with very limited ability to interact outside of itself. One of J2EE’s major disadvantages is that the choice of the platform dictates the use of a single programming language, and a programming language that is not well suited for most businesses. One of J2EE’s major advantages is that most of the J2EE vendors do offer operating system portability.
Microsoft’s .NET platform vision is a family of products rather than specifications, with specifications used primarily to define points of interoperability. The major disadvantage of this approach is that if is limited to the Windows platform, so applications written for the .NET platform can only be run on .NET platforms. Their are several important advantages to the .NET platform:
* The cost of developing applications is much lower, since standard business languages can be used and device independent presentation tier logic can be written.
* The cost of running applications is much lower, since commodity hardware platforms (at 1/5 the cost of their Unix counterparts) can be used.
* The ability to scale up is much greater, with the proved ability to support at least ten times the number of clients any J2EE platform has shown itself able to support.
* Interoperability is much stronger, with industry standard eCollaboration built into the platform.
What’s the difference between System.String and System.StringBuilder classes?
A: System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
What’s the difference between an interface and abstract class?
A: In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
And if they have conflicting method names?
A: It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
What are three test cases you should go through in unit testing?
A: Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
What’s the difference between the Debug class and Trace class?
A; Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
How’s the DLL Hell problem solved in .NET?
A: Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
Can multiple catch blocks be executed?
A: It’s a delegate that points to and eventually fires off several methods.
What’s the difference between const and readonly?
A: You can initialize readonly variables to some runtime values. Let’s say your program uses current date and time as one of the values that won’t change. This way you declare public readonly string DateT = new DateTime().ToString().
What’s the difference between Java and .NET garbage collectors?
A: Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you’re using. Microsoft standardized on their garbage collection.
What are the types of authentication in .net?
A: We have three types of authentication:
. Form authenticatio
. Windows authentication
. Passport This has to be declared in web.config file.
What is difference between constants, readonly and, static ?
A: Constants: The value can’t be changed
Read-only: The value will be initialized only once from the constructor of the class.
Static: Value can be initialized once.
What is the difference between a Struct and a Class ?
A: The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is less expensive. When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will remain unassigned and the object cannot be used until all of the fields are initialized. It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always provided to initialize the struct members to their default values.
It is an error to initialize an instance field in a struct.
There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.
A struct is a value type, while a class is a reference type.
What is Reference type and value type ?
A: Reference Type: Reference types are allocated on the managed CLR heap, just like object types. A data type that is stored as a reference to the value’s location. The value of a reference type is the location of the sequence of bits that represent the type’s data. Reference types can be self-describing types, pointer types, or interface types
Value Type: Value types are allocated on the stack just like primitive types in VBScript, VB6 and C/C++. Value types are not instantiated using new go out of scope when the function they are defined within returns.
Value types in the CLR are defined as types that derive from system.valueType.
A data type that fully describes a value by specifying the sequence of bits that constitutes the value’s representation. Type information for a value type instance is not stored with the instance at run time, but it is available in metadata. Value type instances can be treated as objects using boxing.
What is MSIL, IL, CTS and, CLR ?
A: MSIL: (Microsoft intermediate language) When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Before code can be executed, MSIL must be converted to CPU-specific code, usually by a just-in-time (JIT) compiler. Because the common language runtime supplies one or more JIT compilers for each computer architecture it supports, the same set of MSIL can be JIT-compiled and executed on any supported architecture. When a compiler produces MSIL, it also produces metadata. Metadata describes the types in your code, including the definition of
each type, the signatures of each type’s members, the members that our code references, and other data that the runtime uses at execution time. The MSIL and metadata are contained in a portable executable (PE) file that is based on and extends the published Microsoft PE and Common Object File Format (COFF) used historically for executable content. This file format, which accommodates
MSIL or native code as well as metadata, enables the operating system to recognize common language runtime images. The presence of metadata in the file along with the MSIL enables your code to describe itself, which means that there is no need for type libraries or Interface Definition Language (IDL). The runtime locates and extracts the metadata from the file as needed during execution.
IL: (Intermediate Language)A language used as the output of a number of compilers and as the input to a just-in-time (JIT) compiler. The common language runtime includes a JIT compiler for converting MSIL to native code.
CTS: (Common Type System) The specification that determines how the common language runtime defines, uses, and manages types
CLR: (Common Language Runtime) The engine at the core of managed code execution. The runtime supplies managed code with services such as cross-language integration, code access security, object lifetime management, and debugging and profiling support.
Differnce between Managed code and unmanaged code ?
A: Managed Code: Code that runs under a “contract of cooperation” with the common language runtime. Managed code must supply the metadata necessary for the runtime to provide services such as memory management, cross-language integration, code access security, and automatic lifetime control of objects. All code based on Microsoft intermediate language (MSIL) executes as managed code.
Un-Managed Code:Code that is created without regard for the conventions and requirements of the common language runtime. Unmanaged code executes in the common language runtime environment with minimal services (for example, no garbage collection, limited debugging, and so on).
How can I stop my code being reverse-engineered from IL?
A: There is currently no simple way to stop code being reverse-engineered from IL. In future it is likely that IL obfuscation tools will become available, either from MS or from third parties. These tools work by ‘optimising’ the IL in such a way that reverse-engineering becomes much more difficult. Of course if you are writing web services then reverse-engineering is not a problem as clients do not have access to your IL.
Why is XmlSerializer so slow?
A: There is a once-per-process-per-type overhead with XmlSerializer. So the first time you serialize or deserialize an object of a given type in an application, there is a significant delay. This normally doesn’t matter, but it may mean, for example, that XmlSerializer is a poor choice for loading configuration settings during startup of a GUI application.
What are attributes?
A: There are at least two types of .NET attribute. The first type I will refer to as a metadata attribute - it allows some data to be attached to a class or method. This data becomes part of the metadata for the class, and (like other class metadata) can be accessed via reflection. The other type of attribute is a context attribute. Context attributes use a similar syntax to metadata attributes but they are fundamentally different. Context attributes provide an interception mechanism whereby instance activation and method calls can be
pre- and/or post-processed.
Can I customise the serialization process?
A: Yes. XmlSerializer supports a range of attributes that can be used to configure serialization for a particular class. For example, a field or property can be marked with the [XmlIgnore] attribute to exclude it from serialization. Another example is the [XmlElement]
attribute, which can be used to specify the XML element name to be used for a particular property or field.
Serialization via SoapFormatter/BinaryFormatter can also be controlled to some extent by attributes. For example, the [NonSerialized] attribute is the equivalent of XmlSerializer’s [XmlIgnore] attribute. Ultimate control of the serialization process can be acheived by implementing the the ISerializable interface on the class whose instances are to be serialized.
What is serialization?
A: Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization / Deserialization is mostly used to transport objects (e.g. during remoting), or to persist
objects (e.g. to a file or database).
Is the lack of deterministic destruction in .NET a problem?
A: It’s certainly an issue that affects component design. If you have objects that maintain expensive or scarce resources (e.g. database locks), you need to provide some way for the client to tell the object to release the resource when it is done. Microsoft recommend that you provide a method called Dispose() for this purpose. However, this causes problems for distributed objects - in a distributed system who calls the Dispose() method? Some form of reference-counting or ownership-management mechanism is needed to handle distributed objects - unfortunately the runtime offers no help with this.
Why doesn’t the .NET runtime offer deterministic destruction?
A: Because of the garbage collection algorithm. The .NET garbage collector works by periodically running through a list of all the objects that are currently being referenced by an application. All the objects that it doesn’t find during this search are ready to be destroyed and the memory reclaimed. The implication of this algorithm is that the runtime doesn’t get notified immediately when the final reference on an object goes away - it only finds out during the next sweep of the heap.
Futhermore, this type of algorithm works best by performing the garbage collection sweep as rarely as possible. Normally heap exhaustion is the trigger for a collection sweep.
What is side-by-side execution?
A: Can two application one using private assembly and other using Shared assembly be stated as a side-by-side executables? Side-by-side execution is the ability to run multiple versions of an application or component on the same computer. You can have multiple versions of the common language runtime, and multiple versions of applications and components that use a version of the runtime, on the same computer at the same time. Since versioning is only applied to shared assemblies, and not to private assemblies, two application one using private assembly and one using shared assembly cannot be stated as side-by-side
executables.
Why only boxed types can be unboxed?
A: Unboxing is the process of converting a Reference type variable to Value type and thus allocating memory on the stack . It happens only to those Reference type variables that have been earlier created by Boxing of a Value Type , therefore internally they contain a value type , which can be obtained through explicit casting . For any other Reference type , they don’t internally contain a Value type to Unboxed via explicit casting . This is why only boxed types can be unboxed .
What is the use of Internal keyword?
A: Internal keyword is one of the access specifier available in .Net framework , that makes a type visible in a given assembly , for e.g : a single dll can contain multiple modules , essentially a multi file assembly , but it forms a single binary component , so any type with internal keyword will be visible throughout the assembly and can be used in any of the modules .
Explain the differences between public, protected, private and internal.
A: These all are access modifier and they governs the access level. They can be applied to class, methods, fields.
Public: Allows class, methods, fields to be accessible from anywhere i.e. within and outside an assembly.
Private: When applied to field and method allows to be accessible within a class.
Protected: Similar to private but can be accessed by members of derived class also.
Internal: They are public within the assembly i.e. they can be accessed by anyone within an assembly but outside assembly they are not visible.
Explain the importance and use of each, Version, Culture and PublicKeyToken for an assembly.
A: This three alongwith name of the assembly provide a strong name or fully qualified name to the assembly. When a assebly is referenced with all three.
PublicKeyToken: Each assembly can have a public key embedded in its manifest that identifies the developer. This ensures that once the assembly ships, no one can modify the code or other resources contained in the assembly.
Culture: Specifies which culture the assembly supports
Version: The version number of the assembly.It is of the following form major.minor.build.revision.
What is FullTrust? Do GAC’ed assemblies have FullTrust?
A; fore the .NET Framework existed, Windows had two levels of trust for downloaded code. This old model was a binary trust model. You only had two choices: Full Trust, and No Trust. The code could either do anything you could do, or it wouldn’t run at all.
The permission sets in .NET include FullTrust, SkipVerification, Execution, Nothing, LocalIntranet, Internet and Everything. Full Trust Grants unrestricted permissions to system resources. Fully trusted code run by a normal, nonprivileged user cannot do administrative tasks, but can access any resources the user can access, and do anything the user can do. From a security standpoint, you can think of fully trusted code as being similar to native, unmanaged code, like a traditional ActiveX control.
GAC assemblies are granted FullTrust. In v1.0 and 1.1, the fact that assemblies in the GAC seem to always get a FullTrust grant is actually a side effect of the fact that the GAC lives on the local machine. If anyone were to lock down the security policy by changing the grant set of the local machine to something less than FullTrust, and if your assembly did not get extra permission from some other code group, it would no longer have FullTrust even though it lives in the GAC.
What are PDBs? Where must they be located for debugging to work?
A: A program database (PDB) files holds debugging and project state information that allows incremental linking of debug configuration of your program.There are several different types of symbolic debugging information. The default type for Microsoft compiler is the so-called PDB file. The compiler setting for creating this file is /Zi, or /ZI for C/C++(which creates a PDB file with additional information that enables a feature called “”Edit and Continue”") or a Visual Basic/C#/JScript .NET program with /debug.
A PDB file is a separate file, placed by default in the Debug project subdirectory, that has the same name as the executable file with the extension .pdb. Note that the Visual C++ compiler by default creates an additional PDB file called VC60.pdb for VisulaC++6.0 and VC70.PDB file for VisulaC++7.0. The compiler creates this file during compilation of the source code, when the compiler isn’t aware of the final name of the executable. The linker can merge this temporary PDB file into the main one if you tell it to, but it won’t do it by default. The PDB file can be useful to display the detailed stack trace with source files and line numbers.
How is the using() pattern useful? What is IDisposable? How does it support deterministic finalization?
A; The using() pattern is useful because it ensures that Dispose() will always be called when a disposable object (defined as one that implements IDisposable, and thus the Dispose() method) goes out of scope, even if it does so by an exception being thrown, and thus that resources are always released.
What is the difference between Finalize() and Dispose()?
A: Dispose() is called by the user of an object to indicate that he is finished with it, enabling that object to release any unmanaged resources it holds. Finalize() is called by the run-time to allow an object which has not had Dispose() called on it to do the same. However
Dispose() operates determinalistically, whereas there is no guarantee that Finalize() will be called immediately when an object goes out of scope - or indeed at all, if the program ends before that object is GCed - and as such Dispose() is generally preferred.
How does the generational garbage collector in the .NET CLR manage object lifetime?
What is non-deterministic finalization?
A: The hugely simplistic version is that every time it garbage-collects, it starts by assuming everything to be garbage, then goes through and builds a list of everything reachable. Those become not-garbage, everything else doesn’t, and gets thrown away. What makes it generational is that every time an object goes through this process and survives, it is noted as being a member of an older generation (up to 2, right now). When the garbage-collector is trying to free memory, it starts with the lowest generation (0) and only works up to higher ones if it can’t free up enough space, on the grounds that shorter-lived objects are more likely to have been freed than longer-lived ones.
Non-deterministic finalization implies that the destructor (if any) of an object will not necessarily be run (nor its memory cleaned up, but that’s a relatively minor issue) immediately upon its going out of scope. Instead, it will wait until first the garbage collector gets around to finding it, and then the finalisation queue empties down to it; and if the process ends before this happens, it may not be finalised at all. (Although the operating system will usually clean up any process-external resources left open - note the usually there, especially as the exceptions tend to hurt a lot.)
The PID (Process ID) a unique number for each item on the Process Tab, Image Name list. How do you get the PID to appear?
A: In Task Manger, select the View menu, then select columns and check PID (Process Identifier).In Linux, PID is used to debug a process explicitly. However we cannot do this in a windows environment.
Microsoft has launched a SDK called as Microsoft Operations Management (MOM). This uses the PID to find out which dll’s have been loaded by a process in the memory. This is essentially helpful in situations where the Process which has a memory leak is to be traced to a erring dll. Personally I have never used a PID, our Windows debugger does the things required to find out.
What is a PID? How is it useful when troubleshooting a system?
A: PID is the process Id of the application in Windows. Whenever a process starts running in the Windows environment, it is associated with an individual process Id or PID.
Describe the difference between a Thread and a Process?
A: A Process is an instance of an running application. And a thread is the Execution stream of the Process. A process can have multiple Thread.
When a process starts a specific memory area is allocated to it. When there is multiple thread in a process, each thread gets a memory for storing the variables in it and plus they can access to the global variables which is common for all the thread. Eg.A Microsoft Word is a Application. When you open a word file,an instance of the Word starts and a process is allocated to this instance which has one thread.
Difference between int and int32 ?
A: Both are same. System.Int32 is a .NET class. Int is an alias name for System.Int32.
Can a nested object be used in Serialization ?
A; Yes. If a class that is to be serialized contains references to objects of other classes, and if those classes have been marked as serializable, then their objects are serialized too.
Describe the advantages of writing a managed code application instead of unmanaged one. What’s involved in certain piece of code being managed?
A: “Advantage includes automatic garbage collection,memory management,security,type checking,versioning
Managed code is compiled for the .NET run-time environment. It runs in the Common Language Runtime (CLR), which is the heart of the .NET Framework. The CLR provides services such as security,memory management, and cross-language integration. Managed applications written to take advantage of the features of the CLR perform more efficiently and safely, and take better advantage of developers existing expertise in languages that support the .NET Framework.
Unmanaged code includes all code written before the .NET Framework was introduced—this includes code written to use COM, native Win32, and Visual Basic 6. Because it does not run inside the .NET environment, unmanaged code cannot make use of any .NET managed facilities.”
What is inline schema, how does it works?
A: Schemas can be included inside of XML file is called Inline Schemas.This is useful when it is inconvenient to physically seprate the schema and the XML document.A schema is an XML document that defines the structure, constraints, data types, and relationships of the elements that constitute the data contained inside the XML document or in another XML document.Schema can be an external file which uses the XSD or XDR extension called external schema. Inline schema can take place even when validation is turned off.
Why do you need to serialize.?
A: We need to serialize the object,if you want to pass object from one computer/application domain to another.Process of converting complex objects into stream of bytes that can be persisted or transported.Namespace for serialization is System.Runtime.Serialization.The ISerializable interface allows you to make any class Serializable..NET framework features 2 serializing method.
1.Binary Serialization
2.XML Serialization
What is GUID and why we need to use it and in what condition? How this is created.
A: A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated. Visual Studio .NET IDE has a utility under the tools menu to generate GUIDs.
What is encapsulation ?
A: Encapsulation is the ability to hide the internal workings of an object’s behavior and its data. For instance, let’s say you have a object named Bike and this object has a method named start(). When you create an instance of a Bike object and call its start() method you are not worried about what happens to accomplish this, you just want to make sure the state of the bike is changed to ‘running’ afterwards. This kind of behavior hiding is encapsulation and it makes programming much easier.
Difference between Dispose and Finallize method?
A: Finalize method is used to free the memory used by some unmanaged resources like window handles (HWND). It’s similar to the destructor syntax in C#. The GC calls this method when it founds no more references to the object. But, In some cases we may need release the memory used by the resources explicitely.To release the memory explicitly we need to implement the Dispose method of IDisposable interface.
Whate are Resource Files ? How are they used in .NET?
A: Resource files are the files containing data that is logically deployed with an application.These files can contain data in a number of formats including strings, images and persisted objects. It has the main advantage of If we store data in these files then we don’t need to compile these if the data get changed. In .NET we basically require them storing culture specific informations by localizing application’s resources. You can deploy your resources using satellite assemblies.
What is Globalizationa and Localization ?
A: Globalization is the process of creating an application that meets the needs of users from multiple cultures. It includes using the correct
currency, date and time format, calendar, writing direction, sorting rules, and other issues. Accommodating these cultural differences in an application is called localization.Using classes of System.Globalization namespace, you can set application’s current culture.
This can be achieved by using any of the following 3 approaches.
1.Detect and redirect
2.Run-time adjustment
3.Using Satellite assemblies.
What is managed and unmanaged code?
A: The .NET framework provides several core run-time services to the programs that run within it - for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. i.e., code executing under the control of the CLR is called managed code. For example, any code written in C# or Visual Basic .NET is managed code. Code that runs outside the CLR is referred to as “unmanaged code.” COM components, ActiveX components, and Win32 API functions are examples of unmanaged code.
What is the property available to check if the page posted or not?
A: The Page_Load event handler in the page checks for IsPostBack property value, to ascertain whether the page is posted. The Page.IsPostBack gets a value indicating whether the page is being loaded in response to the client postback, or it is for the first time. The value of Page.IsPostBack is True, if the page is being loaded in response to the client postback; while its value is False, when the page is loaded for the first time. The Page.IsPostBack property facilitates execution of certain routine in Page_Load, only once (for e.g. in Page load, we need to set default value in controls, when page is loaded for the first time. On post back, we check for true value for IsPostback value and then invoke server-side code to update data).
Changes to which portion of version number indicates an incompatible change?
A: Major or minor. Changes to the major or minor portion of the version number indicate an incompatible change. Under this convention then, version 2.0.0.0 would be considered incompatible with version 1.0.0.0. Examples of an incompatible change would be a change to the types of some method parameters or the removal of a type or method altogether. Build. The Build number is typically used to distinguish between daily builds or smaller compatible releases. Revision. Changes to the revision number are typically reserved for an incremental build needed to fix a particular bug. You’ll sometimes hear this referred to as the “emergency bug fix” number in that the revision is what is often changed when a fix to a specific bug is shipped to a customer.
What is Partial Assembly References?
A: Full Assembly reference: A full assembly reference includes the assembly’s text name, version, culture, and public key token (if the assembly has a strong name). A full assembly reference is required if you reference any assembly that is part of the common language runtime or any assembly located in the global assembly cache.
What is the difference between Finalize and Dispose (Garbage collection) ?
A: Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object. In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object.
Dispose can be called even if other references to the object are alive. Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from
permanently leaking if the programmer fails to call Dispose.
What is reflection?
A; All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly.
Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember ) , or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).
What does ‘managed’ mean in the .NET context?
A: The term ‘managed’ is the cause of much confusion. It is used in various places within .NET, meaning slightly different things.Managed code: The .NET framework provides several core run-time services to the programs that run within it - for example
exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime.
Such code is called managed code. All C# and Visual Basic.NET code is managed by default. VS7 C++ code is not managed by default, but the compiler can produce managed code by specifying a command-line switch (/com+).
Managed data: This is data that is allocated and de-allocated by the .NET runtime’s garbage collector. C# and VB.NET data is always managed. VS7 C++ data is unmanaged by default, even when using the /com+ switch, but it can be marked as managed using the __gc keyword.Managed classes: This is usually referred to in the context of Managed Extensions (ME) for C++. When using ME C++, a class can be marked with the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector, but it also means more than that. The class becomes a fully paid-up member of the .NET community with the benefits and restrictions that brings. An example of a benefit is proper interop with classes written in other languages - for example, a managed C++ class can inherit from a VB class. An example of a restriction is that a managed class can only inherit from one base class.
What is IL?
A: IL = Intermediate Language. Also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code (of any language) is compiled to IL. The IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In-Time (JIT) compiler.
What is the CLS?
A: CLS = Common Language Specification. This is a subset of the CTS which all .NET languages are expected to support. The idea is that any program which uses CLS-compliant types can interoperate with any .NET program written in any language.
In theory this allows very tight interop between different .NET languages - for example allowing a C# class to inherit from a VB class.
What is the CTS?
A: CTS = Common Type System. This is the range of types that the .NET runtime understands, and therefore that .NET applications can use. However note that not all .NET languages will support all the types in the CTS. The CTS is a superset of the CLS.
What is the CLR?
A: CLR = Common Language Runtime. The CLR is a set of standard resources that (in theory) any .NET program can take advantage of, regardless of programming language. Robert Schmidt (Microsoft) lists the following CLR resources in his MSDN PDC# article:Object-oriented programming model (inheritance, polymorphism, exception handling, garbage collection) Security model Type system All .NET base classes
Many .NET framework classes Development, debugging, and profiling tools Execution and code management IL-to-native translators and optimizers What this means is that in the .NET world, different programming languages will be more equal in capability than they have ever been before, although clearly not all languages will support all CLR services.
When was the first version of .NET released?
A: The final version of the 1.0 SDK and runtime was made publicly available around 6pm PST on 15-Jan-2002. At the same time, the final version of Visual Studio.NET was made available to MSDN subscribers.
When was .NET announced?
A: Bill Gates delivered a keynote at Forum 2000, held June 22, 2000, outlining the .NET ‘vision’. The July 2000 PDC had a number of sessions on .NET technology, and delegates were given CDs containing a pre-release version of the .NET framework/SDK and Visual Studio.NET.
What happens in memory when you Box and Unbox a value-type?
A: Boxing converts a value-type to a reference-type, thus storing the object on the heap. Unboxing converts a reference-type to a value-type, thus storing the value on the stack.
When should you call the garbage collector in .NET?
A: As a good rule, you should not call the garbage collector. However, you could call the garbage collector when you are done using a large object (or set of objects) to force the garbage collector to dispose of those very large objects from memory. However, this is usually not a good practice.
What is a satellite assembly?
A: When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is the DLL Hell problem solved in .NET?
A: Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
How you will set the datarelation between two columns?
A: ADO.NET provides DataRelation object to set relation between two columns.It helps to enforce the following constraints,a unique constraint, which guarantees that a column in the table contains no duplicates and a foreign-key constraint,which can be used to maintain referential integrity.A unique constraint is implemented either by simply setting the Unique property of a data column to true, or by adding an instance of the UniqueConstraint class to the DataRelation object’s ParentKeyConstraint. As part of the foreign-key constraint, you can specify referential integrity rules that are applied at three points,when a parent record is updated,when a parent record is deleted and when a change is accepted or rejected.
Is Your Glass Half Full?
A; There are three common techniques for managing what happens when users try to modify the same data at the same time: pessimistic, optimistic, and last-in wins. They each handle concurrency issues differently.
The pessimistic approach says: “Nobody can cause a concurrency violation with my data if I do not let them get at the data while I have it.” This tactic prevents concurrency in the first place but it limits scalability because it prevents all concurrent access. Pessimistic concurrency generally locks a row from the time it is retrieved until the time updates are flushed to the database. Since this requires a connection to remain open during the entire process, pessimistic concurrency cannot successfully be implemented in a disconnected model like the ADO.NET DataSet, which opens a connection only long enough to populate the DataSet then releases and closes, so a database lock cannot be held.
Another technique for dealing with concurrency is the last-in wins approach. This model is pretty straightforward and easy to implement-whatever data modification was made last is what gets written to the database. To implement this technique you only need to put the primary key fields of the row in the UPDATE statement’s WHERE clause. No matter what is changed, the UPDATE statement will overwrite the changes with its own changes since all it is looking for is the row that matches the primary key values. Unlike the pessimistic model, the last-in wins approach allows users to read the data while it is being edited on screen. However, problems can occur when users try to modify the same data at the same time because users can overwrite each other’s changes without being notified of the collision. The last-in wins approach does not detect or notify the user of violations because it does not care. However the optimistic technique does detect violations.
In optimistic concurrency models, a row is only locked during the update to the database. Therefore the data can be retrieved and updated by other users at any time other than during the actual row update operation. Optimistic concurrency allows the data to be read simultaneously by multiple users and blocks other users less often than its pessimistic counterpart, making it a good choice for ADO.NET. In optimistic models, it is important to implement some type of concurrency violation detection that will catch any additional attempt to modify records that have already been modified but not committed. You can write your code to handle the violation by always rejecting and canceling the change request or by overwriting the request based on some business rules. Another way to handle the concurrency violation is to let the user decide what to do. The sample application that is shown in Figure 1 illustrates some of the options that can be presented to the user in the event of a concurrency violation.
Explain the ADO . Net Architecture ( .Net Data Provider)
A: ADO.Net is the data access model for .Net –based applications. It can be used to access relational database systems such as SQL SERVER 2000, Oracle, and many other data sources for which there is an OLD DB or ODBC provider. To a certain extent, ADO.NET represents the latest evolution of ADO technology. However, ADO.NET introduces some major changes and innovations that are aimed at the loosely coupled and inherently disconnected – nature of web applications.
A .Net Framework data provider is used to connecting to a database, executing commands, and retrieving results. Those results are either processed directly, or placed in an ADO.NET DataSet in order to be exposed to the user in an ad-hoc manner, combined with data from multiple sources, or remoted between tiers. The .NET Framework data provider is designed to be lightweight, creating a minimal layer between the data source and your code, increasing performance without sacrificing functionality.
Following are the 4 core objects of .Net Framework Data provider:
• Connection: Establishes a connection to a specific data source
• Command: Executes a command against a data source. Exposes Parameters and can execute within the scope of a Transaction from a Connection.
• DataReader: Reads a forward-only, read-only stream of data from a data source.
• DataAdapter: Populates a DataSet and resolves updates with the data source.
The .NET Framework includes the .NET Framework Data Provider for SQL Server (for Microsoft SQL Server version 7.0 or later), the .NET Framework Data Provider for OLE DB, and the .NET Framework Data Provider for ODBC.
The .NET Framework Data Provider for SQL Server: The .NET Framework Data Provider for SQL Server uses its own protocol to communicate with SQL Server. It is lightweight and performs well because it is optimized to access a SQL Server directly without adding an OLE DB or Open Database Connectivity (ODBC) layer. The following illustration contrasts the .NET Framework Data Provider for SQL Server with the .NET Framework Data Provider for OLE DB. The .NET Framework Data Provider for OLE DB communicates to an OLE DB data source through both the OLE DB Service component, which provides connection pooling and transaction services, and the OLE DB Provider for the data source
The .NET Framework Data Provider for OLE DB: The .NET Framework Data Provider for OLE DB uses native OLE DB through COM interoperability to enable data access. The .NET Framework Data Provider for OLE DB supports both local and distributed transactions. For distributed transactions, the .NET Framework Data Provider for OLE DB, by default, automatically enlists in a transaction and obtains transaction details from Windows 2000 Component Services.
The .NET Framework Data Provider for ODBC: The .NET Framework Data Provider for ODBC uses native ODBC Driver Manager (DM) through COM interoperability to enable data access. The ODBC data provider supports both local and distributed transactions. For distributed transactions, the ODBC data provider, by default, automatically enlists in a transaction and obtains transaction details from Windows 2000 Component Services.
The .NET Framework Data Provider for Oracle: The .NET Framework Data Provider for Oracle enables data access to Oracle data sources through Oracle client connectivity software. The data provider supports Oracle client software version 8.1.7 and later. The data provider supports both local and distributed transactions (the data provider automatically enlists in existing distributed transactions, but does not currently support the EnlistDistributedTransaction method).
The .NET Framework Data Provider for Oracle requires that Oracle client software (version 8.1.7 or later) be installed on the system before you can use it to connect to an Oracle data source.
.NET Framework Data Provider for Oracle classes are located in the System.Data.OracleClient namespace and are contained in the System.Data.OracleClient.dll assembly. You will need to reference both the System.Data.dll and the System.Data.OracleClient.dll when compiling an application that uses the data provider.
Choosing a .NET Framework Data Provider
.NET Framework Data Provider for SQL Server: Recommended for middle-tier applications using Microsoft SQL Server 7.0 or later. Recommended for single-tier applications using Microsoft Data Engine (MSDE) or Microsoft SQL Server 7.0 or later.
Recommended over use of the OLE DB Provider for SQL Server (SQLOLEDB) with the .NET Framework Data Provider for OLE DB. For Microsoft SQL Server version 6.5 and earlier, you must use the OLE DB Provider for SQL Server with the .NET Framework Data Provider for OLE DB.
.NET Framework Data Provider for OLE DB: Recommended for middle-tier applications using Microsoft SQL Server 6.5 or earlier, or any OLE DB provider. For Microsoft SQL Server 7.0 or later, the .NET Framework Data Provider for SQL Server is recommended. Recommended for single-tier applications using Microsoft Access databases. Use of a Microsoft Access database for a middle-tier application is not recommended.
.NET Framework Data Provider for ODBC: Recommended for middle-tier applications using ODBC data sources. Recommended for single-tier applications using ODBC data sources.
.NET Framework Data Provider for Oracle: Recommended for middle-tier applications using Oracle data sources. Recommended for single-tier applications using Oracle data sources. Supports Oracle client software version 8.1.7 and later. The .NET Framework Data Provider for Oracle classes are located in the System.Data.OracleClient namespace and are contained in the System.Data.OracleClient.dll assembly. You need to reference both the System.Data.dll and the System.Data.OracleClient.dll when compiling an application that uses the data provider.
Explain acid properties?.
A: The term ACID conveys the role transactions play in mission-critical applications. Coined by transaction processing pioneers, ACID stands for atomicity, consistency, isolation, and durability.
These properties ensure predictable behavior, reinforcing the role of transactions as all-or-none propositions designed to reduce the management load when there are many variables.
Atomicity
A transaction is a unit of work in which a series of operations occur between the BEGIN TRANSACTION and END TRANSACTION statements of an application. A transaction executes exactly once and is atomic — all the work is done or none of it is.
Operations associated with a transaction usually share a common intent and are interdependent. By performing only a subset of these operations, the system could compromise the overall intent of the transaction. Atomicity eliminates the chance of processing a subset of operations.
Consistency
A transaction is a unit of integrity because it preserves the consistency of data, transforming one consistent state of data into another consistent state of data.
Consistency requires that data bound by a transaction be semantically preserved. Some of the responsibility for maintaining consistency falls to the application developer who must make sure that all known integrity constraints are enforced by the application. For example, in developing an application that transfers money, you should avoid arbitrarily moving decimal points during the transfer.
Isolation
A transaction is a unit of isolation — allowing concurrent transactions to behave as though each were the only transaction running in the system.
Isolation requires that each transaction appear to be the only transaction manipulating the data store, even though other transactions may be running at the same time. A transaction should never see the intermediate stages of another transaction.
Transactions attain the highest level of isolation when they are serializable. At this level, the results obtained from a set of concurrent transactions are identical to the results obtained by running each transaction serially. Because a high degree of isolation can limit the number of concurrent transactions, some applications reduce the isolation level in exchange for better throughput.
Durability
A transaction is also a unit of recovery. If a transaction succeeds, the system guarantees that its updates will persist, even if the computer crashes immediately after the commit. Specialized logging allows the system’s restart procedure to complete unfinished operations, making the transaction durable.
What is a pre-requisite for connection pooling?
A; Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical.
Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted?
A; Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
What is the wildcard character in SQL?
A: Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’
What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
A; SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. OLE-DB.NET is a .NET layer on top of the OLE layer, so it’s not as fastest and efficient as SqlServer.NET.
What is the role of the DataReader class in ADO.NET connections?
A: It returns a read-only, forward-only rowset from the data source. A DataReader provides fast access when a forward-only sequential read is needed.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
A: The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels range from None to Verbose, allowing you to fine-tune the tracing activities.
What does assert() method do?
A: In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
Can you declare an override method to be static if the original method is not static?
A: No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)
How is method overriding different from method overloading?
A: When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class
What is the difference between a Struct and a Class?
A: Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
What’s the difference between an interface and abstract class?
A: In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
What happens if you inherit multiple interfaces and they have conflicting method names?
A: It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
To Do: Investigate
Explain the three services model commonly know as a three-tier application.
A: Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
Can multiple catch blocks be executed for a single try statement?
A: No. Once the proper catch block processed, control is transferred to the finally block (if there are any)
What’s the C# syntax to catch any possible exception?
A: A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
A: The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element’s object, resulting in a different, yet identacle object.
What’s the advantage of using System.Text.StringBuilder over System.String?
A: StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.
What does the term immutable mean?
A: The data value may not be changed. Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
Are private class-level variables inherited?
A: Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
Who is a protected class-level variable available to?
A: It is available to any sub-class (a class inheriting this class).
What is a Windows Service and how does its lifecycle differ from a “standard” EXE?
A: Windows service is a application that runs in the background. It is equivalent to a NT service.
The executable created is not a Windows application, and hence you can’t just click and run it . it needs to be installed as a service, VB.Net has a facility where we can add an installer to our program and then use a utility to install the service. Where as this is not the case with standard exe
Can you create an app domain?
A; Yes, We can create user app domain by calling on of the following overload static methods of the System.AppDomain class
1. Public static AppDomain CreateDomain(String friendlyName)
2. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo)
3. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info)
4. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, String appBasePath, String appRelativeSearchPath, bool shadowCopyFiles)
What is the difference between Server.Transfer and Response.Redirect?
A: Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist across the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.
Response.Dedirect() :client knows the physical location (page name and query string as well). Context.Items loses the persistence when navigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites,
What does the term immutable mean?
A: The data value may not be changed. Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
Are private class-level variables inherited?
A: Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
Who is a protected class-level variable available to?
A: It is available to any sub-class (a class inheriting this class).
What is a Windows Service and how does its lifecycle differ from a “standard” EXE?
A: Windows service is a application that runs in the background. It is equivalent to a NT service.
The executable created is not a Windows application, and hence you can’t just click and run it . it needs to be installed as a service, VB.Net has a facility where we can add an installer to our program and then use a utility to install the service. Where as this is not the case with standard exe
Can you create an app domain?
A; Yes, We can create user app domain by calling on of the following overload static methods of the System.AppDomain class
1. Public static AppDomain CreateDomain(String friendlyName)
2. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo)
3. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info)
4. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, String appBasePath, String appRelativeSearchPath, bool shadowCopyFiles)
What is the difference between Server.Transfer and Response.Redirect?
A: Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist across the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.
Response.Dedirect() :client knows the physical location (page name and query string as well). Context.Items loses the persistence when navigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
Response.Redirect sends a response to the client browser instructing it to request the second page. This requires a round-trip to the client, and the client initiates the Request for the second page. Server.Transfer transfers the process to the second page without making a round-trip to the client. It also transfers the HttpContext to the second page, enabling the second page access to all the values in the HttpContext of the first page.
How do you implement Paging in .Net?
A: The DataGrid provides the means to display a group of records from the data source (for example, the first 10), and then navigate to the “page” containing the next 10 records, and so on through the data.
Using Ado.Net we can explicit control over the number of records returned from the data source, as well as how much data is to be cached locally in the DataSet.
1.Using DataAdapter.fill method give the value of ‘Maxrecords’ parameter (Note: - Don’t use it because query will return all records but fill the dataset based on value of ‘maxrecords’ parameter).
2.For SQL server database, combines a WHERE clause and a ORDER BY clause with TOP predicate.
3.If Data does not change often just cache records locally in DataSet and just take some records from the DataSet to display.
What is the difference between HTTP-Post and HTTP-Get?
A: As their names imply, both HTTP GET and HTTP POST use HTTP as their underlying protocol. Both of these methods encode request parameters as name/value pairs in the HTTP request.
The GET method creates a query string and appends it to the script’s URL on the server that handles the request.
The POST method creates a name/value pairs that are passed in the body of the HTTP request message.
What is the difference between in-proc and out-of-proc?
A: An inproc is one which runs in the same process area as that of the client giving tha advantage of speed but the disadvantage of stability becoz if it crashes it takes the client application also with it.Outproc is one which works outside the clients memory thus giving stability to the client, but we have to compromise a bit on speed.
What are the various ways of securing a web site that could prevent from hacking etc .. ?
A: 1) Authentication/Authorization
2) Encryption/Decryption
3) Maintaining web servers outside the corporate firewall. etc.,
What is validationsummary server control?where it is used?.
A: The ValidationSummary control allows you to summarize the error messages from all validation controls on a Web page in a single location. The summary can be displayed as a list, a bulleted list, or a single paragraph, based on the value of the DisplayMode property. The error message displayed in the ValidationSummary control for each validation control on the page is specified by the ErrorMessage property of each validation control. If the ErrorMessage property of the validation control is not set, no error message is displayed in the ValidationSummary control for that validation control. You can also specify a custom title in the heading section of the ValidationSummary control by setting the HeaderText property. You can control whether the ValidationSummary control is displayed or hidden by setting the ShowSummary property. The summary can also be displayed in a message box by setting the ShowMessageBox property to true.
What is ViewState ? and how it is managed ?
A: ASP.NET ViewState is a new kind of state service that developers can use to track UI state on a per-user basis. Internally it uses an an old Web programming trick-roundtripping state in a hidden form field and bakes it right into the page-processing framework.It needs less code to write and maintain state in your Web-based forms.
What are different templates available in Repeater,DataList and Datagrid ?
A: Templates enable one to apply complicated formatting to each of the items displayed by a control.Repeater control supports five types of templates.HeaderTemplate controls how the header of the repeater control is formatted.ItemTemplate controls the formatting of each item displayed.AlternatingItemTemplate controls how alternate items are formatted and the SeparatorTemplate displays a separator between each item displyed.FooterTemplate is used for controlling how the footer of the repeater control is formatted.The DataList and Datagrid supports two templates in addition to the above five.SelectedItem Template controls how a selected item is formatted and EditItemTemplate controls how an item selected for editing is formatted.
” ?">When do you set “” ?
A: Identity is a webconfig declaration under System.web, which helps to control the application Identity of the web applicaton. Which can be at any level (Machine,Site, application, subdirectory , or page) , attribute impersonate with “true” as value specifies that client impersonation is used.
How do you register JavaScript for webcontrols ?
A: You can register javascript for controls using Attribtues.Add(scriptname,scripttext) method.
Which two properties are on every validation control?
A: We have two common properties for every validation controls
1. Control to Validate,
2. Error Message.
How do you create a permanent cookie?
A; Permanent cookies are the ones that are most useful. Permanent cookies are available until a specified expiration date, and are stored on the hard disk. The location of cookies differs with each browser, but this doesn’t matter, as this is all handled by your browser and the server. If you want to create a permanent cookie called Name with a value of Nigel, which expires in one month, you’d use the following code
Response.Cookies (”Name”) = “Nigel” Response.Cookies (”Name”). Expires = DateAdd (”m”, 1, Now ())
How do you turn off cookies for one page in your site?
A: Use Cookie.Discard property, Gets or sets the discard flag set by the server. When true, this property instructs the client application not to save the Cookie on the user’s hard disk when a session ends.
What method do you use to explicitly kill a user s session?
A: You can dump (Kill) the session yourself by calling the method Session.Abandon.
ASP.NET automatically deletes a user’s Session object, dumping its contents, after it has been idle for a configurable timeout interval. This interval, in minutes, is set in the section of the web.config file. The default is 20 minutes.
What are the advantages and disadvantages of viewstate?
A: The primary advantages of the ViewState feature in ASP.NET are:
1. Simplicity. There is no need to write possibly complex code to store form data between page submissions.
2. Flexibility. It is possible to enable, configure, and disable ViewState on a control-by-control basis, choosing to persist the values of some fields but not others.
There are, however a few disadvantages that are worth pointing out:
1. Does not track across pages. ViewState information does not automatically transfer from page to page. With the session approach, values can be stored in the session and accessed from other pages. This is not possible with ViewState, so storing data into the session must be done explicitly.
2. ViewState is not suitable for transferring data for back-end systems. That is, data still has to be transferred to the back end using some form of data object.
Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?
A: The Application_Start event is guaranteed to occur only once throughout the lifetime of the application. It’s a good place to initialize global variables. For example, you might want to retrieve a list of products from a database table and place the list in application state or the Cache object. SessionStateModule exposes both Session_Start and Session_End events.
Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component?
A: Communicating through a Firewall When building a distributed application with 100s/1000s of users spread over multiple locations, there is always the problem of communicating between client and server because of firewalls and proxy servers. Exposing your middle tier components as Web Services and invoking the directly from a Windows UI is a very valid option.
• Application Integration When integrating applications written in various languages and running on disparate systems. Or even applications running on the same platform that have been written by separate vendors.
• Business-to-Business Integration This is an enabler for B2B intergtation which allows one to expose vital business processes to authorized supplier and customers. An example would be exposing electronic ordering and invoicing, allowing customers to send you purchase orders and suppliers to send you invoices electronically.
• Software Reuse This takes place at multiple levels. Code Reuse at the Source code level or binary componet-based resuse. The limiting factor here is that you can reuse the code but not the data behind it. Webservice overcome this limitation. A scenario could be when you are building an app that aggregates the functionality of serveral other Applicatons. Each of these functions could be performed by individual apps, but there is value in perhaps combining the the multiple apps to present a unifiend view in a Portal or Intranet.
•When not to use Web Services: Single machine Applicatons When the apps are running on the same machine and need to communicate with each other use a native API. You also have the options of using component technologies such as COM or .NET Componets as there is very little overhead.
•Homogeneous Applications on a LAN If you have Win32 or Winforms apps that want to communicate to their server counterpart. It is much more efficient to use DCOM in the case of Win32 apps and .NET Remoting in the case of .NET Apps
What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
A: Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist accros the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.
Response.Dedirect() :client know the physical location (page name and query string as well). Context.Items loses the persisitance when nevigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
What does the “EnableViewState” property do? Why would I want it on or off?
A: Enable ViewState turns on the automatic state management feature that enables server controls to re-populate their values on a round trip without requiring you to write any code. This feature is not free however, since the state of a control is passed to and from the server in a hidden form field. You should be aware of when ViewState is helping you and when it is not. For example, if you are binding a control to data on every round trip, then you do not need the control to maintain it’s view state, since you will wipe out any re-populated data in any case. ViewState is enabled for all server controls by default. To disable it, set the EnableViewState property of the control to false.
Should validation (did the user enter a real date) occur server-side or client-side? Why?
A: It should occur both at client-side and Server side.By using expression validator control with the specified expression ie.. the regular expression provides the facility of only validatating the date specified is in the correct format or not. But for checking the date where it is the real data or not should be done at the server side, by getting the system date ranges and checking the date whether it is in between that range or not.
How do you create a permanent cookie?
A: Permanent cookies are available until a specified expiration date, and are stored on the hard disk.So Set the ‘Expires’ property any value greater than DataTime.MinValue with respect to the current datetime. If u want the cookie which never expires set its Expires property equal to DateTime.maxValue.
What is different b/w webconfig.xml & Machineconfig.xml
A: Web.config & machine.config both are configuration files.Web.config contains settings specific to an application where as machine.config contains settings to a computer. The Configuration system first searches settings in machine.config file & then looks in application configuration files.Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies configuration settings to its own directory and all child directories below it. There is only Machine.config file on a web server.
If I’m developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is spanned across three web-servers (using round-robbin load balancing) what would be the best approach to maintain login-in state for the users?
Use the state server or store the state in the database. This can be easily done through simple setting change in the web.config.
StateConnectionString="tcpip=127.0.0.1:42424"
sqlConnectionString="data source=127.0.0.1; user id=sa; password="
cookieless="false"
timeout="30" />
You can specify mode as “stateserver” or “sqlserver”.
Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one
“One of ASP.NET’s most useful features is the extensibility of the HTTP pipeline, the path that data takes between client and server. You can use them to extend your ASP.NET applications by adding pre- and post-processing to each HTTP request coming into your application. For example, if you wanted custom authentication facilities for your application, the best technique would be to intercept the request when it comes in and process the request in a custom HTTP module.
What event handlers can I include in Global.asax?
A: Application_Start,Application_End, Application_AcquireRequestState, Application_AuthenticateRequest, Application_AuthorizeRequest, Application_BeginRequest, Application_Disposed, Application_EndRequest, Application_Error, Application_PostRequestHandlerExecute, Application_PreRequestHandlerExecute,
Application_PreSendRequestContent, Application_PreSendRequestHeaders, Application_ReleaseRequestState, Application_ResolveRequestCache, Application_UpdateRequestCache, Session_Start,Session_End
You can optionally include “On” in any of method names. For example, you can name a BeginRequest event handler.Application_BeginRequest or Application_OnBeginRequest.You can also include event handlers in Global.asax for events fired by custom HTTP modules.Note that not all of the event handlers make sense for Web Services (they’re designed for ASP.NET applications in general, whereas .NET XML Web Services are specialized instances of an ASP.NET app). For example, the Application_AuthenticateRequest and Application_AuthorizeRequest events are designed to be used with ASP.NET Forms authentication.
How can you provide an alternating color scheme in a Repeater control?
A: AlternatingItemTemplate Like the ItemTemplate element, but rendered for every other row (alternating items) in the Repeater control. You can specify a different appearance for the AlternatingItemTemplate element by setting its style properties.
What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
A: In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they’re difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems.
As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.
What are ASP.NET Web Forms? How is this technology different than what is available though ASP?
A: Web Forms are the heart and soul of ASP.NET. Web Forms are the User Interface (UI) elements that give your Web applications their look and feel. Web Forms are similar to Windows Forms in that they provide properties, methods, and events for the controls that are placed onto them. However, these UI elements render themselves in the appropriate markup language required by the request, e.g. HTML. If you use Microsoft Visual Studio .NET, you will also get the familiar drag-and-drop interface used to create your UI for your Web application.
What type of code (server or client) is found in a Code-Behind class?
A: Client-side validation because there is no need to request a server side date when you could obtain a date from the client machine.
Explain the differences between Server-side and Client-side code?
A: Server side scripting means that all the script will be executed by the server and interpreted as needed. ASP doesn’t have some of the functionality like sockets, uploading, etc. For these you have to make a custom components usually in VB or VC++. Client side scripting means that the script will be executed immediately in the browser such as form field validation, clock, email validation, etc. Client side scripting is usually done in VBScript or JavaScript. Download time, browser compatibility, and visible code - since JavaScript and VBScript code is included in the HTML page, then anyone can see the code by viewing the page source. Also a possible security hazards for the client computer.
What does AspCompat=”true” mean and when should I use it?
A: AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects–that is, COM objects registered ThreadingModel=Apartment. That includes all COM objects written with Visual Basic 6.0. AspCompat should also be set to true (regardless of threading model) if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true:
Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available to the COM components by placing unmanaged wrappers around the equivalent ASP.NET objects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the request for the page) and the COM objects it creates share an apartment. AspCompat=”true” forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel=Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat=”true,” request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it’s marshaled across apartment boundaries.
Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don’t access ASP intrinsic objects and that are registered ThreadingModel=Free or ThreadingModel=Both.
How does dynamic discovery work?
A: ASP.NET maps the file name extension VSDISCO to an HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document. A client who requests a VSDISCO file gets back what appears to be a static DISCO document.
Note that VSDISCO files are disabled in the release version of ASP.NET. You can reenable them by uncommenting the line in the section of Machine.config that maps *.vsdisco to System.Web.Services.Discovery.DiscoveryRequestHandler and granting the ASPNET user account permission to read the IIS metabase. However, Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security.
How do I send e-mail from an ASP.NET application?
A: MailMessage message = new MailMessage ();
message.From = ;
message.To = ;
message.Subject = “Scheduled Power Outage”;
message.Body = “Our servers will be down tonight.”;
SmtpMail.SmtpServer = “localhost”;
SmtpMail.Send (message);
MailMessage and SmtpMail are classes defined in the .NET Framework Class Library’s System.Web.Mail namespace. Due to a security change made to ASP.NET just before it shipped, you need to set SmtpMail’s SmtpServer property to “localhost” even though “localhost” is the default. In addition, you must use the IIS configuration applet to enable localhost (127.0.0.1) to relay messages through the local SMTP service.
Is it necessary to lock application state before accessing it?
A: Only if you’re performing a multistep update and want the update to be treated as an atomic operation. Here’s an example:
Application.Lock ();
Application[”ItemsSold”] = (int) Application[”ItemsSold”] + 1;
Application[”ItemsLeft”] = (int) Application[”ItemsLeft”] - 1;
Application.UnLock ();
By locking application state before updating it and unlocking it afterwards, you ensure that another request being processed on another thread doesn’t read application state at exactly the wrong time and see an inconsistent view of it. If I update session state, should I lock it, too? Are concurrent accesses by multiple requests executing on multiple threads a concern with session state? Concurrent accesses aren’t an issue with session state, for two reasons. One, it’s unlikely that two requests from the same user will overlap. Two, if they do overlap, ASP.NET locks down session state during request processing so that two threads can’t touch it at once. Session state is locked down when the HttpApplication instance that’s processing the request fires an AcquireRequestState event and unlocked when it fires a ReleaseRequestState event.
Can a user browsing my Web site read my Web.config or Global.asax files?
A: No. The section of Machine.config, which holds the master configuration settings for ASP.NET, contains entries that map ASAX files, CONFIG files, and selected other file types to an HTTP handler named HttpForbiddenHandler, which fails attempts to retrieve the associated file. You can modify it by editing Machine.config or including an section in a local Web.config file.
How do I debug an ASP.NET application that wasn’t written with Visual Studio.NET and that doesn’t use code-behind?
A: Start the DbgClr debugger that comes with the .NET Framework SDK, open the file containing the code you want to debug, and set your breakpoints. Start the ASP.NET application. Go back to DbgClr, choose Debug Processes from the Tools menu, and select aspnet_wp.exe from the list of processes. (If aspnet_wp.exe doesn’t appear in the list,check the “Show system processes” box.) Click the Attach button to attach to aspnet_wp.exe and begin debugging.
Be sure to enable debugging in the ASPX file before debugging it with DbgClr. You can enable tell ASP.NET to build debug executables by placing a
statement at the top of an ASPX file or a statement in a Web.config file.
What are different types of directives in .NET?
A: @Page: Defines page-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .aspx files
@Control:Defines control-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .ascx files.
@Import: Explicitly imports a namespace into a page or user control. The Import directive cannot have more than one namespace attribute. To import multiple namespaces, use multiple @Import directives.
@Implements: Indicates that the current page or user control implements the specified .NETframework interface.
@Register: Associates aliases with namespaces and class names for concise notation in custom server control syntax.
@Assembly: Links an assembly to the current page during compilation, making all the assembly’s classes and interfaces available for use on the page.
@OutputCache: Declaratively controls the output caching policies of an ASP.NET page or a user control contained in a page
@Reference: Declaratively indicates that another user control or page source file should be dynamically compiled and linked against the page in which this directive is declared.
What do you mean by authentication and authorization?
A: Authentication is the process of validating a user on the credentials (username and password) and authorization performs after authentication. After Authentication a user will be verified for performing the various tasks, Its access is limited it is known as authorization.
What are the different types of caching?
A: Caching is a technique widely used in computing to increase performance by keeping frequently accessed or expensive data in memory. In context of web application, caching is used to retain the pages or data across HTTP requests and reuse them without the expense of recreating them. ASP.NET has 3 kinds of caching strategies Output Caching, Fragment Caching, Data Caching.
Output Caching: Caches the dynamic output generated by a request. Some times it is useful to cache the output of a website even for a minute, which will result in a better performance. For caching the whole page the page should have OutputCache directive.
Fragment Caching: Caches the portion of the page generated by the request. Some times it is not practical to cache the entire page, in such cases we can cache a portion of page
Data Caching: Caches the objects programmatically. For data caching asp.net provides a cache object for eg: cache[”States”] = dsStates;
What methods are fired during the page load?
A: Init() When the page is instantiated, Load() - when the page is loaded into server memory,PreRender () - the brief moment before the page is displayed to the user as HTML, Unload() - when page finishes loading.
What is view state and use of it?
A: The current property settings of an ASP.NET page and those of any ASP.NET server controls contained within the page. ASP.NET can detect when a form is requested for the first time versus when the form is posted (sent to the server), which allows you to program accordingly.
What are the validation controls?
A: set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation using client script.
What are user controls and custom controls?
A: Custom controls: A control authored by a user or a third-party software vendor that does not belong to the .NET Framework class library. This is a generic term that includes user controls. A custom server control is used in Web Forms (ASP.NET pages). A custom client control is used in Windows Forms applications.
User Controls: In ASP.NET: A user-authored server control that enables an ASP.NET page to be re-used as a server control. An ASP.NET user control is authored declaratively and persisted as a text file with an .ascx extension. The ASP.NET page framework compiles a user control on the fly to a class that derives from the System.Web.UI.UserControl class.
What are the different types of assemblies available and their purpose?
A: Private, Public/shared and Satellite Assemblies.
Private Assemblies : Assembly used within an application is known as private assemblies.
Public/shared Assemblies : Assembly which can be shared across applicaiton is known as shared assemblies. Strong Name has to be created to create a shared assembly. This can be done using SN.EXE. The same has to be registered using GACUtil.exe (Global Assembly Cache).
What is the difference between Value Types and Reference Types?
A: Value Types uses Stack to store the data where as the later uses the Heap to store the data.
What is Boxing and UnBoxing?
A: Boxing is implicit conversion of ValueTypes to Reference Types (Object). UnBoxing is explicit conversion of Reference Types (Object) to its equivalent ValueTypes. It requires type-casting.
What are the different types of Session state management options available with ASP.NET?
A: ASP.NET provides In-Process and Out-of-Process state management. In-Process stores the session in memory on the web server. This requires the a “sticky-server” (or no load-balancing) so that the user is always reconnected to the same web server. Out-of-Process Session state management stores data in an external data source. The external data source may be either a SQL Server or a State Server service. Out-of-Process state management requires that all objects stored in session are serializable.
What does the “EnableViewState” property do? Why would I want it on or off?
A: It allows the page to save the users input on a form across postbacks. It saves the server-side values for a given control into ViewState, which is stored as a hidden value on the page before sending the page to the clients browser. When the page is posted back to the server the server control is recreated with the state stored in viewstate.
What is the lifespan for items stored in ViewState?
A: Item stored in ViewState exist for the life of the current page. This includes postbacks (to the same page).
What is ViewState?
A: ViewState allows the state of objects (serializable) to be stored in a hidden field on the page. ViewState is transported to the client and back to the server, and is not stored on the server or any other external source. ViewState is used to retain the state of server-side objects between post backs.
Can you edit data in the Repeater control?
A: No, it just reads the information from its data source.
Which method do you invoke on the DataAdapter control to load your generated dataset with data?
A: The Fill() method.
Whats MSIL, and why should my developers need an appreciation of it if at all?
A: MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL. MSIL also allows the .NET Framework to JIT compile the assembly on the installed computer.
Explain what a diffgram is, and a good use for one?
A: The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML. A good use is reading database data to an XML file to be sent to a Web Service.
Describe the difference between inline and code behind.
A: Inline code written along side the html in a page. Code-behind is code written in a separate file and referenced by the .aspx page
Can you explain what inheritance is and an example of when you might use it?
A: When you want to inherit (use the functionality of) another class. Example: With a base class named Employee, a Manager class could be derived from the Employee base class.
What are the Application_Start and Session_Start subroutines used for?
A: This is where you can set the specific variables for the Application and Session objects
What is the Global.asax used for?
A: The Global.asax (including the Global.asax.cs file) is used to implement application and session level events.
Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
A: Valid answers are:
• A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
• A DataSet is designed to work without any continuing connection to the original data source.
• Data in a DataSet is bulk-loaded, rather than being loaded on demand.
• There’s no concept of cursor types in a DataSet.
• DataSets have no current record pointer You can use For Each loops to move through the data.
• You can store many edits in a DataSet, and write them to the original data source in a single operation.
• Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.
What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
A: Server.Transfer transfers page processing from one page directly to the next page without making a round-trip back to the client’s browser. This provides a faster response with a little less overhead on the server. Server.Transfer does not update the clients url history list or current url. Response.Redirect is used to redirect the user’s browser to another page or site. This perform as a trip back to the client where the client’s browser is redirected to the new page. The user’s browser history list is updated to reflect the new address.
Should user input data validation occur server-side or client-side? Why?
A: All user input data validation should occur on the server at a minimum. Additionally, client-side validation can be performed where deemed appropriate and feasable to provide a richer, more responsive experience for the user.
What type of code (server or client) is found in a Code-Behind class?
A: The answer is server-side code since code-behind is executed on the server. However, during the code-behind’s execution on the server, it can render client-side code such as JavaScript to be processed in the clients browser. But just to be clear, code-behind executes on the server, thus making it server-side code.
Suppose you want a certain ASP.NET function executed on MouseOver for a certain button. Where do you add an event handler?
A: Add an OnMouseOver attribute to the button. Example: btnSubmit.Attributes.Add(”onmouseover”,”someClientCodeHere();”);
What’s a bubbled event?
A: When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their event handlers, allowing the main DataGrid event handler to take care of its constituents.
When during the page processing cycle is ViewState available?
A: After the Init() and before the Page_Load(), or OnLoad() for a control.
What methods are fired during the page load?
A: Init() - when the page is instantiated
Load() - when the page is loaded into server memory
PreRender() - the brief moment before the page is displayed to the user as HTML
Unload() - when page finishes loading.
What’s the difference between Response.Write() and Response.Output.Write()?
A: Response.Output.Write() allows you to write formatted output.
Describe the role of inetinfo.exe, aspnet_isapi.dll and aspnet_wp.exe in the page loading process ?
A: inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things. When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request to the actual worker process aspnet_wp.exe.
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