.Net Interview Questions

What is serialization in .NET? What are the ways to control serialization?

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).Serialization can be defined as the process of storing the state of an object to a storage medium. During this process, the public and private fields of the object and the name of the class, including the assembly containing the class, are converted to a stream of bytes, which is then written to a data stream. When the object is subsequently deserialized, an exact clone of the original object is created.
• Binary serialization preserves type fidelity, which is useful for preserving the state of an object between different invocations of an application. For example, you can share an object between different applications by serializing it to the clipboard. You can serialize an object to a stream, disk, memory, over the network, and so forth. Remoting uses serialization to pass objects "by value" from one computer or application domain to another.
• XML serialization serializes only public properties and fields and does not preserve type fidelity. This is useful when you want to provide or consume data without restricting the application that uses the data. Because XML is an open standard, it is an attractive choice for sharing data across the Web. SOAP is an open standard, which makes it an attractive choice.
There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code.

Why do I get errors when I try to serialize a Hashtable?

XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction.

What is exception handling?

When an exception occurs, the system searches for the nearest catch clause that can handle the exception, as determined by the run-time type of the exception. First, the current method is searched for a lexically enclosing try statement, and the associated catch clauses of the try statement are considered in order. If that fails, the method that called the current method is searched for a lexically enclosing try statement that encloses the point of the call to the current method. This search continues until a catch clause is found that can handle the current exception, by naming an exception class that is of the same class, or a base class, of the run-time type of the exception being thrown. A catch clause that doesn't name an exception class can handle any exception.
Once a matching catch clause is found, the system prepares to transfer control to the first statement of the catch clause. Before execution of the catch clause begins, the system first executes, in order, any finally clauses that were associated with try statements more nested that than the one that caught the exception.
Exceptions that occur during destructor execution are worth special mention. If an exception occurs during destructor execution, and that exception is not caught, then the execution of that destructor is terminated and the destructor of the base class (if any) is called. If there is no base class (as in the case of the object type) or if there is no base class destructor, then the exception is discarded.

What is Assembly?

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.
Assemblies are a fundamental part of programming with the .NET Framework. An assembly performs the following functions:
• It contains code that the common language runtime executes. Microsoft intermediate language (MSIL) code in a portable executable (PE) file will not be executed if it does not have an associated assembly manifest. Note that each assembly can have only one entry point (that is, DllMain, WinMain, or Main).
• It forms a security boundary. An assembly is the unit at which permissions are requested and granted.
• It forms a type boundary. Every type's identity includes the name of the assembly in which it resides. A type called MyType loaded in the scope of one assembly is not the same as a type called MyType loaded in the scope of another assembly.
• It forms a reference scope boundary. The assembly's manifest contains assembly metadata that is used for resolving types and satisfying resource requests. It specifies the types and resources that are exposed outside the assembly. The manifest also enumerates other assemblies on which it depends.
• It forms a version boundary. The assembly is the smallest versionable unit in the common language runtime; all types and resources in the same assembly are versioned as a unit. The assembly's manifest describes the version dependencies you specify for any dependent assemblies.
• It forms a deployment unit. When an application starts, only the assemblies that the application initially calls must be present. Other assemblies, such as localization resources or assemblies containing utility classes, can be retrieved on demand. This allows applications to be kept simple and thin when first downloaded.
• It is the unit at which side-by-side execution is supported.
Assemblies can be static or dynamic. Static assemblies can include .NET Framework types (interfaces and classes), as well as resources for the assembly (bitmaps, JPEG files, resource files, and so on). Static assemblies are stored on disk in PE files. You can also use the .NET Framework to create dynamic assemblies, which are run directly from memory and are not saved to disk before execution. You can save dynamic assemblies to disk after they have executed.
There are several ways to create assemblies. You can use development tools, such as Visual Studio .NET, that you have used in the past to create .dll or .exe files. You can use tools provided in the .NET Framework SDK to create assemblies with modules created in other development environments. You can also use common language runtime APIs, such as Reflection.Emit, to create dynamic assemblies.

What are the contents of assembly?

In general, a static assembly can consist of four elements:
• The assembly manifest, which contains assembly metadata.
• Type metadata.
• Microsoft intermediate language (MSIL) code that implements the types.
• A set of resources.

What are the different types of assemblies?

Private, Public/Shared, Satellite

What is the difference between a private assembly and a shared assembly?

Location and visibility: A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. the .NET framework classes.
Versioning: The runtime enforces versioning constraints only on shared assemblies, not on private assemblies.

What are Satellite Assemblies? How you will create this? How will you get the different language strings?

Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific assemblies work in side-by-side execution because the application has a separate product ID for each language and installs satellite assemblies in a language-specific subdirectory for each language. When uninstalling, the application removes only the satellite assemblies associated with a given language and .NET Framework version. No core .NET Framework files are removed unless the last language for that .NET Framework version is being removed.
(For example, English and Japanese editions of the .NET Framework version 1.1 share the same core files. The Japanese .NET Framework version 1.1 adds satellite assemblies with localized resources in a \ja subdirectory. An application that supports the .NET Framework version 1.1, regardless of its language, always uses the same core runtime files.)

What is Assembly manifest? what all details the assembly manifest will contain?

Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the assembly relate to each other. The assembly manifest contains this assembly metadata. An assembly manifest contains all the metadata needed to specify the assembly's version requirements and security identity, and all metadata needed to define the scope of the assembly and resolve references to resources and classes. The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a standalone PE file that contains only assembly manifest information.
It contains Assembly name, Version number, Culture, Strong name information, List of all files in the assembly, Type reference information, Information on referenced assemblies.
Difference between assembly manifest & metadata?
assembly manifest - An integral part of every assembly that renders the assembly self-describing. The assembly manifest contains the assembly's metadata. The manifest establishes the assembly identity, specifies the files that make up the assembly implementation, specifies the types and resources that make up the assembly, itemizes the compile-time dependencies on other assemblies, and specifies the set of permissions required for the assembly to run properly. This information is used at run time to resolve references, enforce version binding policy, and validate the integrity of loaded assemblies. The self-describing nature of assemblies also helps makes zero-impact install and XCOPY deployment feasible.
metadata - Information that describes every element managed by the common language runtime: an assembly, loadable file, type, method, and so on. This can include information required for debugging and garbage collection, as well as security attributes, marshaling data, extended class and member definitions, version binding, and other information required by the runtime.

What is Global Assembly Cache (GAC) and what is the purpose of it? (How to make an assembly to public? Steps) How more than one version of an assembly can keep in same place?

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. You should share assemblies by installing them into the global assembly cache only when you need to.
Steps
- Create a strong name using sn.exe tool
eg: sn -k keyPair.snk
- with in AssemblyInfo.cs add the generated file name
eg: [assembly: AssemblyKeyFile("abc.snk")]
- recompile project, then install it to GAC by either
drag & drop it to assembly folder (C:\WINDOWS\assembly OR C:\WINNT\assembly) (shfusion.dll tool)
or
gacutil -i abc.dll

.Net Interview Questins

What is JIT (just in time)? how it works?

Before Microsoft intermediate language (MSIL) can be executed, it must be converted by a .NET Framework just-in-time (JIT) compiler to native code, which is CPU-specific code that runs on the same computer architecture as the JIT compiler.
Rather than using time and memory to convert all the MSIL in a portable executable (PE) file to native code, it converts the MSIL as it is needed during execution and stores the resulting native code so that it is accessible for subsequent calls.
The runtime supplies another mode of compilation called install-time code generation. The install-time code generation mode converts MSIL to native code just as the regular JIT compiler does, but it converts larger units of code at a time, storing the resulting native code for use when the assembly is subsequently loaded and executed.
As part of compiling MSIL to native code, code must pass a verification process unless an administrator has established a security policy that allows code to bypass verification. Verification examines MSIL and metadata to find out whether the code can be determined to be type safe, which means that it is known to access only the memory locations it is authorized to access.


What is strong name?
A name that consists of an assembly's identity—its simple text name, version number, and culture information (if provided)—strengthened by a public key and a digital signature generated over the assembly.

What is portable executable (PE)?
The file format defining the structure that all executable files (EXE) and Dynamic Link Libraries (DLL) must use to allow them to be loaded and executed by Windows. PE is derived from the Microsoft Common Object File Format (COFF). The EXE and DLL files created using the .NET Framework obey the PE/COFF formats and also add additional header and data sections to the files that are only used by the CLR. The specification for the PE/COFF file formats is available at http://www.microsoft.com/whdc/hwdev/hardware/pecoffdown.mspx


What is Code Access Security (CAS)?
CAS is the part of the .NET security model that determines whether or not a piece of code is allowed to run, and what resources it can use when it is running. For example, it is CAS that will prevent a .NET web applet from formatting your hard disk.


How does CAS work?
The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set.
For example, using the default security policy, a control downloaded from a web site belongs to the 'Zone - Internet' code group, which adheres to the permissions defined by the 'Internet' named permission set. (Naturally the 'Internet' named permission set represents a very restrictive range of permissions.)

Who defines the CAS code groups?
Microsoft defines some default ones, but you can modify these and even create your own

How do I define my own code group?
Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new code group as a sub-group of the 'Zone - Internet' group, like this:
caspol -ag 1.3 -site www.mydomain.com FullTrust
Now if you run caspol -lg you will see that the new group has been added as group 1.3.1:
...
1.3. Zone - Internet: Internet
1.3.1. Site - www.mydomain.com: FullTrust
...
Note that the numeric label (1.3.1) is just a caspol invention to make the code groups easy to manipulate from the command-line. The underlying runtime never sees it.

How do I change the permission set for a code group?
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.

Can I create my own permission set?
Yes. Use caspol -ap, specifying an XML file containing the permissions in the permission set. To save you some time, here is a sample file corresponding to the 'Everything' permission set - just edit to suit your needs. When you have edited the sample, add it to the range of available permission sets like this:
caspol -ap samplepermset.xml
Then, to apply the permission set to a code group, do something like this:
caspol -cg 1.3 SamplePermSet (By default, 1.3 is the 'Internet' code group)

I'm having some trouble with CAS. How can I diagnose my problem?
Caspol has a couple of options that might help. First, you can ask caspol to tell you what code group an assembly belongs to, using caspol -rsg. Similarly, you can ask what permissions are being applied to a particular assembly using caspol -rsp.

I can't be bothered with all this CAS stuff. Can I turn it off?
Yes, as long as you are an administrator. Just run:
caspol -s off
http://www.codeproject.com/dotnet/UB_CAS_NET.asp

What are object pooling and connection pooling and difference? Where do we set the Min and Max Pool size for connection pooling?
Object pooling is a COM+ service that enables you to reduce the overhead of creating each object from scratch. When an object is activated, it is pulled from the pool. When the object is deactivated, it is placed back into the pool to await the next request. You can configure object pooling by applying the ObjectPoolingAttribute attribute to a class that derives from the System.EnterpriseServices.ServicedComponent class.
Object pooling lets you control the number of connections you use, as opposed to connection pooling, where you control the maximum number reached.
Following are important differences between object pooling and connection pooling:
• Creation. When using connection pooling, creation is on the same thread, so if there is nothing in the pool, a connection is created on your behalf. With object pooling, the pool might decide to create a new object. However, if you have already reached your maximum, it instead gives you the next available object. This is crucial behavior when it takes a long time to create an object, but you do not use it for very long.
• Enforcement of minimums and maximums. This is not done in connection pooling. The maximum value in object pooling is very important when trying to scale your application. You might need to multiplex thousands of requests to just a few objects. (TPC/C benchmarks rely on this.)
COM+ object pooling is identical to what is used in .NET Framework managed SQL Client connection pooling. For example, creation is on a different thread and minimums and maximums are enforced.

What is Application Domain?
The primary purpose of the AppDomain is to isolate an application from other applications. Win32 processes provide isolation by having distinct memory address spaces. This is effective, but it is expensive and doesn't scale well. 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.
Objects in different application domains communicate either by transporting copies of objects across application domain boundaries, or by using a proxy to exchange messages.
MarshalByRefObject is the base class for objects that communicate across application domain boundaries by exchanging messages using a proxy. Objects that do not inherit from MarshalByRefObject are implicitly marshal by value. When a remote application references a marshal by value object, a copy of the object is passed across application domain boundaries.

How does an AppDomain get created?
AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a .NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every application.
AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain, creates an instance of an object inside it, and then executes one of the object's methods. Note that you must name the executable 'appdomaintest.exe' for this code to work as-is.
using System;
using System.Runtime.Remoting;

public class CAppDomainInfo : MarshalByRefObject
{
public string GetAppDomainInfo()
{
return "AppDomain = " + AppDomain.CurrentDomain.FriendlyName;
}
}
public class App
{
public static int Main()
{
AppDomain ad = AppDomain.CreateDomain( "Andy's new domain", null, null );
ObjectHandle oh = ad.CreateInstance( "appdomaintest", "CAppDomainInfo" );
CAppDomainInfo adInfo = (CAppDomainInfo)(oh.Unwrap());
string info = adInfo.GetAppDomainInfo();
Console.WriteLine( "AppDomain info: " + info );
return 0;
}


}

C# interview questions Set 2

1. What’s the implicit name of the parameter that gets passed into the set method/property of a class?

value. The data type of the value parameter is defined by whatever data type the property is declared as.
2. What does the keyword “virtual” declare for a method or property?
The method or property can be overridden.
3. How is method overriding different from method overloading?
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.
4. Can you declare an override method to be static if the original method is non-static?
No. The signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
1. To do: Re-word the answer for better clarity.
5. Can you override private virtual methods?
No. Private methods are not accessible outside the class.
1. Original answer: No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
2. To do: Can a private method even be declared a virtual?
6. What are the different ways a method can be overloaded?
Different parameter data types, different number of parameters, different order of parameters.
7. If a base class has a number of overloaded constructors, and an inherited class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
1. To do: question is to complex. It can be stated better.
8. Why is it a bad idea to throw your own exceptions?
Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block?
Throwing your own exceptions signifies some design flaws in the project.
9. What’s a delegate?
A delegate object encapsulates a reference to a method.
10. What’s a multicast delegate?
It’s a delegate that points to and eventually fires off several methods.
20. How do you inherit from a class in C#?
Place a colon and then the name of the base class.
21. Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.
22. Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.
23. What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
24. When do you absolutely have to declare a class as abstract?
1. When at least one of the methods in the class is abstract.
2. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.
25. What’s an interface class?
It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
26. Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
1. To do: Clean up this answer.
27. Can you inherit multiple interfaces?
Yes, why not.
1. To do: Need a better answer.
28. And if they have conflicting method names?
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.
29. What’s the difference between an interface and abstract class?
In an interface class, all methods must be abstract. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed, which is ok in an abstract class.
30. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack -> additional overhead but faster retrieval. Another difference is that structs CANNOT inherit. (questions courtesy of Eyal)

C# interview questions Set 1

Note: Please naviagate to the other set of questions by clicking the links in the "Other Questions" section on the right hand side

1. Does C# support multiple-inheritance?

No, use interfaces instead.

2. When you inherit a protected class-level variable, who is it available to?

Classes in the same namespace.

3. Are private class-level variables inherited?

Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.

4. Describe the accessibility modifier “protected internal”.

It is available to derived classes and classes within the same Assembly (and
naturally from the base class it’s declared in).

5. C# provides a default class constructor for me. I decide to write a constructor that takes a string as a parameter, but want to keep the constructor that has no parameter. How many constructors should I write?

Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.

6.What’s the top .NET class that everything is derived from?

System.Object.

7. How to implement encapsulation in C#.

Through Properties.

8. What’s the difference between System.String and System.StringBuilder classes?

System.String is immutable. System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

9.What’s the advantage of using System.Text.StringBuilder over System.String?

StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time it’s being operated on, a new instance is created.

10. Can you store multiple data types in System.Array?

No.

12. How can you sort the elements of the array in descending order?

By calling Sort() and then Reverse() methods.

13. What’s the .NET class that allows the retrieval of a data element using a unique key?

HashTable.

14. What class is underneath the SortedList class?

A sorted HashTable.

15. Will the finally block get executed if an exception has not occurred?

Yes.

16. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?

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 {}.

17. Can multiple catch blocks be executed?

No. Once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.

18. Explain the three services model commonly know as a three-tier application.

Presentation (UI), business (logic and underlying code) and data (from storage or other sources).

19. What is the role of the DataReader class in ADO.NET connections?

It returns a read-only dataset from the data source when the command is executed.

Other ASP.Net related interview questions are available at
Set 1 of ASP.Net Interview questions or Asp.Net FAQs
Set 2 of ASP.Net Interview questions or Asp.Net FAQs
Set 3 of ASP.Net Interview questions or ASP.Net FAQs
New features of C# 4.0 is available at C# 4.0 FAQs or C# 4.0
Basic .Net questions are available at .Net Frame works FAQ or .Net interview question
Web Service interview question are available at Web Service Interview questions

Web Service Interview questions

Note: Please naviagate to the other set of questions by clicking the links in the "Other Questions" section on the right hand side

What are web services?
Web Services are business logic components which provide functionality via the Internet using standard protocols such as HTTP. Web Services uses Simple Object Access Protocol (SOAP) in order to expose the business functionality.SOAP defines a standardized format in XML which can be exchanged between two entities over standard protocols such as HTTP. SOAP is platform independent so the consumer of a Web Service is therefore completely shielded from any implementation details about the platform exposing the Web Service. For the consumer it is simply a black box of send and receive XML over HTTP. So any web service hosted on windows can also be consumed by any platform.
cCick on the link to know more about what are web services

What are the communication protocol of Web services?
Web services communcate through SOAP and HTTP protocols. Click on the link to know more about what is soap

What is the format of a SOAP message?
Generally SOAP message has two major sections, Header and Body.

What is UDDI ?
Full form of UDDI is Universal Description, Discovery and Integration. It is a directory that can be used to publish and discover public Web Services. For example tomorrow you wish to pusblish your web site and want to know

What is DISCO ?
DISCO is the abbreviated form of Discovery. It is basically used to club or group common services together on a server and provides links to the schema documents of the services it describes may require

What is WSDL?
Web Service Description Language (WSDL)is a W3C specification which defines XML grammar for describing Web Services.XML grammar describes details such as:- √ Where we can find the Web Service (its URI)? √ What are the methods and properties that service supports? √ Data type support. √ Supported protocols In short its a bible of what the webservice can do.Clients can consume this WSDL and build proxy objects that clients use to communicate with the Web Services. Full WSDL specification is available

What is file extension of Webservices ?
.ASMX is extension for Webservices.

How do you authenticate your web service?
you can use SOAP header to authenticate your web service. You may define a class and added as a SOAP header to the web method. While calling from client this has to be added to the SOAP header and should be passed along with the request.
To here to know more about Authenticating a web service with soap header

Can you overload a web method?
Web methods can be overloaded with the message property of the web method.

What is Web Service Enhancements ?
Web Services Enhancements for Microsoft .NET (WSE) is a .NET class library for building Web services using the latest Web services protocols, including WS-Security, WS-SecureConversation, WS-Trust, and WS-Addressing. WSE allows you to add these capabilities at design time using code or at deployment time through the use of a policy file.

What are the design points to be considered while designing a web service.
The return type of the web service should not be language specific. for exampe if you are building it .Net the return type should not be dataset, rather should be a string or an int which can be understood by all Languages.

Other ASP.Net related interview questions are available at
Set 1 of ASP.Net Interview questions or Asp.Net FAQs
Set 2 of ASP.Net Interview questions or Asp.Net FAQs
Set 3 of ASP.Net Interview questions or ASP.Net FAQs

New features of C# 4.0 is available at C# 4.0 FAQs or C# 4.0
Basic .Net questions are available at .Net Frame works FAQ or .Net interview question

.Net Framework Questions (Set 2)

Note: Please naviagate to the other set of questions by clicking the links in the "Other Questions" section on the right hand side

What is CODE Access security?

.Net Framework provides sceurity at the code level also which is known as code access security (CAS). CAS is part of .NET security model that determines whether or not a piece of code is allowed to run and what resources it can use while running. Example CAS will allow an application to read but not to write and delete a file or a resource from a folder. CAS settings can be done using Caspol.exe tool.

What is a satellite assembly?

When we use the same application for different languages we use resources files (.resx files) to show the same application in different languages. These resources when formed as an assembly are called as satellite assembly.

How to prevent my .NET DLL to be decompiled?

When we compile any .net code it gets compiled in to MSIL. This MSIL code can easily be reverse engineered by using ILDASM tool. However we can prevent the .net dlls to be decompiled by using "obfuscation". For obfuscation we can either use any third part tool or dotfuscator tool provided by Microsoft.

What is the difference between Convert.ToString and .ToString() method ?

The Convert.ToString("") will handle NULL values where as .ToString() will not.

What is Native Image Generator (Ngen.exe)?

The Native Image Generator utility (Ngen.exe) allows you to run the JIT compiler on your assembly's MSIL and generate native machine code which is cached to disk. After the image is created .NET runtime will use the image to run the code rather than from the hard disk. Running Ngen.exe on an assembly potentially allows the assembly to load and execute faster, because it restores code and data structures from the native image cache rather than generating them dynamically.

If we have two version of same assembly in GAC how do we make a choice ?

The choice of version can be made in the config file. Below code shows an example

What is AL (Assembly Linker)?

As you are aware assembly can be of either single file type or it can contain multiple file type. When you want to add a file to assembly you can use assebmly linker.

What are the key elements of an assembly?

Portable Executable header , Metadata, MSIL

How many manifest an assembly can have?

One

What are Generations in Garbage collection.

Garbage collection has 3 generations. Generation 0, Generation 1 and Generation 2. When the object is first created it is created in the Generatin 0. When the garbage collector runs it clears the unused memories and pushes the objects that are in use to Generation 1. This way Garbage collector makes more space for the new objects in Generation 0. When the Generation 1 is full again it runs and moves the unused items to generation 2. The objects in Generation 0 are newly created and the one in Generation 1 are the oldest.

Other ASP.Net related interview questions are available at
Set 1 of ASP.Net Interview questions or Asp.Net FAQs

Set 2 of ASP.Net Interview questions or Asp.Net FAQs
Set 3 of ASP.Net Interview questions or ASP.Net FAQs
New features of C# 4.0 is available at
C# 4.0 FAQs or C# 4.0

Basic .Net questions are available at
.Net Frame works FAQ or .Net interview question

.Net Framework Questions (Set 1)

Note: Every set is having 20 questions each. Please naviagate to the other set of questions by clicking the links in the "Other Questions" section on the right hand side

What is IL or MSIL?
Intermediate Language is also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code is compiled to IL. This 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 a CLR?
Full form of CLR is Common Language Runtime and it forms the heart of the .NET framework. All Languages have runtime and its the responsibility of the runtime to take care of the code execution of the program. For example VC++ has MSCRT40.DLL,VB6 has MSVBVM60.DLL, Java has Java Virtual Machine etc. Similarly .NET has CLR. Following are the responsibilities of CLR
* Garbage Collection :- CLR automatically manages memory thus eliminating memory leaks. When objects are not referred GC automatically releases those memories thus providing efficient memory management.
* Code Access Security :- CAS grants rights to program depending on the security configuration of the machine. Example the program has rights to edit or create a new file but the security configuration of machine does not allow the program to delete a file. CAS will take care that the code runs under the environment of machines security configuration.
* Code Verification :- This ensures proper code execution and type safety while the code runs. It prevents the source code to perform illegal operation such as accessing invalid memory locations etc.
* IL( Intermediate language )-to-native translators and optimizer’s :- CLR uses JIT and compiles the IL code to machine code and then executes. CLR also determines depending on platform what is optimized way of running the IL code.

What is a CTS?
In order that two language communicate smoothly CLR has CTS (Common Type System).Example in VB you have “Integer” and in C++ you have “long” these datatypes are not compatible so the interfacing between them is very complicated. In order to able that two different languages can communicate Microsoft introduced Common Type System. So “Integer” datatype in VB6 and “int” datatype in C++ will convert it to System.int32 which is datatype of CTS. CLS which is covered in the coming question is subset of CTS.

What is a CLS(Common Language Specification)?
This is a subset of the CTS which all .NET languages are expected to support. It was always a dream of Microsoft to unite all different languages in to one umbrella and CLS is one step towards that. Microsoft has defined CLS which are nothing but guidelines that language to follow so that it can communicate with other .NET languages in a seamless manner.

What is a Managed Code?
Managed code runs inside the environment of CLR i.e. .NET runtime. In short all IL are managed code. But if you are using some third party software example VB6 or VC++ component they are unmanaged code as .NET runtime (CLR) does not have control over the source code execution of the language.

What is an Assembly?
* Assembly is unit of deployment like EXE or a DLL.
* An assembly consists of one or more files (dlls, exe’s, html files etc.), and represents a group of resources, type definitions, and implementations of those types. An assembly may also contain references to other assemblies. These resources, types and references are described in a block of data called a manifest. The manifest is part of the assembly, thus making the assembly self-describing.
* An assembly is completely self-describing. An assembly contains metadata information, which is used by the CLR for everything from type checking and security to actually invoking the components methods. As all information is in the assembly itself, it is independent of registry. This is the basic advantage as compared to COM where the version was stored in registry.
* Multiple versions can be deployed side by side in different folders. These different versions can execute at the same time without interfering with each other. Assemblies can be private or shared. For private assembly deployment, the assembly is copied to the same directory as the client program that references it. No registration is needed, and no fancy installation program is required.70 When the component is removed, no registry cleanup is needed, and no uninstall program is required. Just delete it from the hard drive.
* In shared assembly deployment, an assembly is installed in the Global Assembly Cache (or GAC). The GAC contains shared assemblies that are globally accessible to all .NET applications on the machine.

What are the different types of Assembly?
There are two types of assembly Private and Public assembly. A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. Crystal report classes which will be used by all application for Reports.

What is Namespace?
Namespace has two basic functionalities:-
1. Namespace Logically group types, example System.Web.UI logically groups our UI related features.
2. In Object Oriented world many times it is possible that programmers will use the same class name. By qualifying Namespace with classname this collision can be avoided.

What is Difference between Namespace and Assembly?
Following are the differences between namespace and assembly:
1. Assembly is physical grouping of logical units. Namespace logically groups classes.
2. Namespace can span multiple assemblies.

What is Manifest?
Assembly metadata is stored in Manifest. Manifest contains all the metadata needed to do the following things (See Figure Manifest View for more details):
· Version of assembly
· Security identity
· Scope of the assembly
· Resolve references to resources and classes.
· The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a stand-alone PE file that contains only assembly manifest information.

Where is version information stored of an assembly?
Version information is stored in assembly in manifest.

Is versioning applicable to private assemblies?
Versioning concept is only applicable to global assembly cache (GAC) as private assembly lie in their individual folders.

What is GAC?
GAC (Global Assembly Cache) is used where shared .NET assembly reside. GAC is used in the following situations :-
· If the application has to be shared among several application.
· If the assembly has some special security requirements like only administrators can remove the assembly. If the assembly is private then a simple delete of assembly the assembly file will remove the assembly.

What is garbage collection?
Garbage collection is a CLR feature which automatically manages memory. Programmers forget to release the objects while coding ..... Laziness (Remember in VB6 where one of the good practices is to set object to nothing). CLR automatically releases objects when they are no longer in use and referenced. CLR runs on non-deterministic to see the unused objects and cleans them. One side effect of this non-deterministic feature is that we cannot assume an object is destroyed when it goes out of the scope of a function. we should avoid using destructors because before GC destroys the object it first executes destructor in that case it will have to wait for code to release the unmanaged resource. Result in additional delays in GC. So it is recommended to implement IDisposable interface and write cleaup code in Dispose method and call GC.SuppressFinalize method so instructing GC not to call your constructor.
Can we force garbage collector to run ?
System.GC.Collect() forces garbage collector to run. This is not recommended but can be used if situations arises.

What is reflection?

All .NET assemblies have metadata information stored about the types defined in modules. This metadata information can be accessed by mechanism called as “Reflection”.System. Reflection can be used to browse through the metadata information.

What are different types of JIT?
JIT compiler is a part of the runtime execution environment. In Microsoft .NET there are three types of JIT compilers:
· Pre-JIT :- Pre-JIT compiles complete source code into native code in a single compilation cycle. This is done at the time of deployment of the application.
· Econo-JIT :- Econo-JIT compiles only those methods that are called at runtime. However, these compiled methods are removed when they are not required.
· Normal-JIT :- Normal-JIT compiles only those methods that are called at runtime. These methods are compiled the first time they are called, and then they are stored in cache. When the same methods are called again, the compiled code from cache is used for execution.

What are Value types and Reference types ?
Value types directly contain their data which are either allocated on the stack or allocated in-line in a structure. Reference types store a reference to the value's memory address, and are allocated on the heap. Reference types can be self-describing types, pointer types, or interface types. Variables that are value types each have their own copy of the data, and therefore operations on one variable do not affect other variables. Variables that are reference types can refer to the same object; therefore, operations on one variable can affect the same.

What is concept of Boxing and Unboxing ?
Boxing permits any value type to be implicitly converted to type object or to any interface type implemented by value type. Boxing is a process in which object instances are created and copy values in to that instance. Unboxing is vice versa of boxing operation where the value is copied from the instance in to appropriate storage location. Below is sample code of boxing and unboxing where integer data type is converted in to object and then vice versa.
Dim x As Integer
Dim y As Object
x = 10
‘ boxing process
y = x
‘ unboxing process
x = y

Set 1 of ASP.Net Interview questions or Asp.Net FAQs
Set 2 of ASP.Net Interview questions or Asp.Net FAQs

Set 3 of ASP.Net Interview questions or ASP.Net FAQs

New features of C# 4.0 is available at C# 4.0 FAQs or C# 4.0

Basic .Net questions are available at .Net Frame works FAQ or .Net interview question

C# 4.0 Interview questions

What are the key new features in C# 4.0

The new features in C# 4.0 fall into four groups:
Dynamic lookup
Dynamic lookup allows you to write method, operator and indexer calls, property and field accesses, and even object invocations which bypass the C# static type checking and instead gets resolved at runtime.
Named and optional parameters
Parameters in C# can now be specified as optional by providing a default value for them in a member declaration. When the member is invoked, optional arguments can be omitted. Furthermore, any argument can be passed by parameter name instead of position.
COM specific interop features
Dynamic lookup as well as named and optional parameters both help making programming against COM less painful than today. On top of that, however, we are adding a number of other small features that further improve the interop experience.

What is Named and optional argumnent.

C# 4.0 does not permit you to omit arguments between commas as in M(1,,3). This could lead to highly unreadable comma-counting code. Instead any argument can be passed by name. Thus if you want to omit only y from a call of M you can write:
M(1, z: 3); // passing z by name
or
M(x: 1, z: 3); // passing both x and z by name
or even
M(z: 3, x: 1); // reversing the order of arguments
All forms are equivalent, except that arguments are always evaluated in the order they appear, so in the last example the 3 is evaluated before the 1.
Optional and named arguments can be used not only with methods but also with indexers and constructors.

Other ASP.Net related interview questions are available at

Set 1 of ASP.Net Interview questions or Asp.Net FAQs
Set 2 of ASP.Net Interview questions or Asp.Net FAQs

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Basic .Net questions are available at .Net Frame works FAQ or .Net interview question

ASP.Net interview questions, ASP.Net FAQs (Set 2)

Note: Every set is having 20 questions each. Please naviagate to the other set of questions by clicking the links in the "Other Questions" section on the right hand side

Can a user browsing my Web site read my Web.config or Global.asax files?

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

Is it necessary to lock application state before accessing it?

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.

Do ASP.NET forms authentication cookies provide any protection against replay attacks? Do they, for example, include the client's IP address or anything else that would distinguish the real client from an attacker?

No. If an authentication cookie is stolen, it can be used by an attacker. It's up to you to prevent this from happening by using an encrypted communications channel (HTTPS). Authentication cookies issued as session cookies, do, however,include a time-out valid that limits their lifetime. So a stolen session cookie can only be used in replay attacks as long as the ticket inside the cookie is valid. The default time-out interval is 30 minutes.You can change that by modifying the timeout attribute accompanying the element in Machine.config or a local Web.config file. Persistent authentication cookies do not time-out and therefore are a more serious security threat if stolen.

Is it possible to prevent a browser from caching an ASPX page?

Just call SetNoStore on the HttpCachePolicy object exposed through the Response object's Cache property, as demonstrated here:

<%@ Page Language="C#" %>

<%

Response.Cache.SetNoStore ();

Response.Write (DateTime.Now.ToLongTimeString ());

%>

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 does AspCompat="true" mean and when should I use it?

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:
<%@ Page AspCompat="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.

Which two properties are on every validation control?

We have two common properties for every validation controls 1. Control to Validate,2. Error Message.

What property do you have to set to tell the grid which page to go to when using the Pager object?

CurrentPageIndex

What tag do you use to add a hyperlink column to the DataGrid?

Which method do you use to redirect the user to another page without performing a round trip to the client?

Server.transfer

Explain role based security ?

Role Based Security lets you identify groups of users to allow or deny based on their role in the organization. For example In Windows NT and Windows XP, roles map to names used to identify user groups. Windows defines several built-in groups, including Administrators, Users, and Guests. To allow or deny access to certain groups of users, add the element to the authorization list in your Web application's Web.config file. e.g.

<>

< roles="Domain Name\Administrators">

< !-- Allow Administrators in domain. -- >

< users="*">

< !-- Deny anyone else. -- >

< /authorization >

How do you register JavaScript for webcontrols ?

You can register javascript for controls using

What is web.config file ?

Web.config file is the configuration file for the Asp.net web application. There is one web.config file for one asp.net application which configuresthe particular application. Web.config file is written in XML with specific tags having specific meanings.It includes databa which includesconnections,Session States,Error Handling,Security etc.For example :

<>

<>

< key="ConnectionString" value="server=localhost;uid=sa;pwd=;database=MyDB">

< /appSettings >

< /configuration >

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?

DataTextField and DataValueField

Which control would you use if you needed to make sure the values in two different controls matched?

CompareValidator is used to ensure that two fields are identical.

What is validationsummary server control?where it is used?.

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.

Difference between asp and asp.net?."

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 webapplications."

What are the various ways of securing a web site that could prevent from hacking etc .. ?

1) Authentication/Authorization

2) Encryption/Decryption

3) Maintaining web servers outside the corporate firewall. etc.,

What is the difference between in-proc and out-of-proc?

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.

When you’re running a component within ASP.NET, what process is it running within on Windows XP? Windows 2000? Windows 2003?

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.

Other ASP.Net related interview questions are available at
Set 1 of ASP.Net Interview questions or Asp.Net FAQs
Set 3 of ASP.Net Interview questions or ASP.Net FAQs
New features of C# 4.0 is available at C# 4.0 FAQs or C# 4.0
Basic .Net questions are available at .Net Frame works FAQ or .Net interview question

ASP.Net interview questions, ASP.Net FAQs (Set 1)

Note: Every set is having 20 questions each. Please naviagate to the other set of questions by clicking the links in the "Other Questions" section on the right hand side

What do you mean by authentication and authorization?

Authentication is the process of validating a user on the credentials (username and password) . After Authentication a user will be verified for performing the various tasks, It access is limited it is known as authorization.

What's the difference between Page.RegisterClientScriptBlock and Page.RegisterStartupScript?

RegisterClientScriptBlock is for returning blocks of client-side script containing functions. RegisterStartupScript is for returning blocks of client-script not packaged in functions-in other words, code that's to execute when the page is loaded. The latter positions script blocks near the end of the document so elements on the page that the script interacts are loaded before the script runs.<%@ Reference Control="MyControl.ascx" %>

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's the difference between Response.Write() andResponse.Output.Write()?

The latter one allows you to write formattedoutput.

What methods are fired during the page load?

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 a bubbled event?

When you have a complex control, likeDataGrid, 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.Suppose you want a certain ASP.NET function executed on MouseOver over a certain button.

How do you set a button say "btnSubmit" button to fire a java script function?

It's the Attributesproperty, the Add function inside that property. e.g. btnSubmit.Attributes.Add("onMouseOver","someClientCode();")

What data type does the RangeValidator control support?

Integer,String and Date.

What are the different types of caching?

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 strategiesOutput CachingFragment CachingData
CachingOutput 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.<%@ OutputCache Duration="60" VaryByParam="state" %>
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.

<%@ OutputCache Duration="120" VaryByParam="CategoryID;SelectedID"%>Data Caching: Caches the objects programmatically. For data caching asp.net provides a cache object for eg: cache["States"] = dsStates;

How do I send e-mail from an ASP.NET application?

Using the below code mail can be triggered from a .Net application

MailMessage message = new MailMessage ();

message.From = abc@abc.com;

message.To = xyz@aboc.com;

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.

Explain the differences between Server-side and Client-side code?

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.

Should validation (did the user enter a real date) occur server-side or client-side? Why?

Client-side validation because there is no need to request a server side date when you could obtain a date from the client machine.

What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?

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.

How do you create a permanent cookie?

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 does the "EnableViewState" property do? Why would I want it on or off?

EnableViewState 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.

What event handlers can I include in Global.asax?

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.

Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?

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.

What are the advantages and disadvantages of viewstate?

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 (same 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.

What method do you use to explicitly kill a user s session?

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.

How do you turn off cookies for one page in your site?

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.

Other ASP.Net related interview questions are available at

Set 2 of ASP.Net Interview questions or Asp.Net FAQs

Set 3 of ASP.Net Interview questions or ASP.Net FAQs

New features of C# 4.0 is available at C# 4.0 FAQs or C# 4.0

Basic .Net questions are available at .Net Frame works FAQ or .Net interview question

ASP.Net interview questions, ASP.Net FAQs (Set 3)

Note: Every set is having 20 questions each. Please naviagate to the other set of questions by clicking the links in the "Other Questions" section on the right hand side

What tags do you need to add within the asp:datagrid tags to bind columns manually?
Set AutoGenerateColumns Property to false on the datagrid tag and then use Column tag and an ASP:databound tag
< runat="server" id="ManualColumnBinding" autogeneratecolumns="False"> <>
< headertext="Column1" datafield="Column1">
< headertext="Column2" datafield="Column2"> < /Columns >< /asp:DataGrid >



What does aspnet_regiis -i do ?
Aspnet_regiis.exe is The ASP.NET IIS Registration tool allows an administrator or installation program to easily update the script maps for an ASP.NET application to point to the ASP.NET ISAPI version associated with the tool. The tool can also be used to display the status of all installed versions of ASP. NET, register the ASP.NET version coupled with the tool, create client-script directories, and perform other configuration operations. When multiple versions of the .NET Framework are executing side-by-side on a single computer, the ASP.NET ISAPI version mapped to an ASP.NET application determines which version of the common language runtime is used for the application. The tool can be launched with a set of optional parameters. Option "i" Installs the version of ASP.NET associated with Aspnet_regiis.exe and updates the script maps at the IIS metabase root and below. Note that only applications that are currently mapped to an earlier version of ASP.NET are affected.

What is a PostBack?
The process in which a Web page sends data back to the same page on the server.

What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?
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.

What is the <> element and what two ASP.NET technologies is it used for? Configures keys to use for encryption and decryption of forms authentication cookie data and view state data, and for verification of out-of-process session state identification.There fore 2 ASP.Net technique in which it is used are Encryption/Decryption & Verification.

What three Session State providers are available in ASP.NET 1.1? What are the pros and cons of each?
ASP.NET provides three distinct ways to store session data for your application: in-process session state, out-of-process session state as a Windows service, and out-of-process session state in a SQL Server database. Each has it advantages.
1.In-process session-state modeLimitations: * When using the in-process session-state mode, session-state data is lost if aspnet_wp.exe or the application domain restarts. * If you enable Web garden mode in the <> element of the application's Web.config file, do not use in-process session-state mode. Otherwise, random data loss can occur. Advantage: * in-process session state is by far the fastest solution. If you are storing only small amounts of volatile data in session state, it is recommended that you use the in-process provider.
2. The State Server simply stores session state in memory when in out-of-proc mode. In this mode the worker process talks directly to the State Server
3. SQL mode, session states are stored in a SQL Server database and the worker process talks directly to SQL. The ASP.NET worker processes are then able to take advantage of this simple storage service by serializing and saving (using .NET serialization services) all objects within a client's Session collection at the end of each Web request Both these out-of-process solutions are useful primarily if you scale your application across multiple processors or multiple computers, or where data cannot be lost if a server or process is restarted.

What is the difference between HTTP-Post and HTTP-Get?
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.

Name and describe some HTTP Status Codes and what they express to the requesting client. When users try to access content on a server that is running Internet Information Services (IIS) through HTTP or File Transfer Protocol (FTP), IIS returns a numeric code that indicates the status of the request. This status code is recorded in the IIS log, and it may also be displayed in the Web browser or FTP client. The status code can indicate whether a particular request is successful or unsuccessful and can also reveal the exact reason why a request is unsuccessful. There are 5 groups ranging from 1xx - 5xx of http status codes exists.
101 - Switching protocols.
200 - OK. The client request has succeeded
302 - Object moved.
400 - Bad request.
500.13 - Web server is too busy.

Explain < @OutputCache% > and the usage of VaryByParam, VaryByHeader.
OutputCache is used to control the caching policies of an ASP.NET page or user control. To cache a page @OutputCache directive should be defined as follows < %@ OutputCache Duration="100" VaryByParam="none" % >
VaryByParam: A semicolon-separated list of strings used to vary the output cache. By default, these strings correspond to a query string value sent with GET method attributes, or a parameter sent using the POST method. When this attribute is set to multiple parameters, the output cache contains a different version of the requested document for each specified parameter. Possible values include none, *, and any valid query string or POST parameter name.
VaryByHeader: A semicolon-separated list of HTTP headers used to vary the output cache. When this attribute is set to multiple headers, the output cache contains a different version of the requested document for each specified header.

What is the difference between repeater over datalist and datagrid?
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 <>, and the DataList wraps the contents in either an HTML <> or <> 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

Can we handle the error and redirect to some pages using web.config?
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:
< mode="RemoteOnly" defaultredirect="Customerror.aspx">
< 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 <> 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 hereDim str As System.Text.StringBuilderstr.Append("hi") ' Error Line as str is not instantiatedResponse.Write(str.ToString)End Sub
[Web.Config]
< mode="On" defaultredirect="Error.aspx">' a simple redirect will take the user to Error.aspx [user defined] error file.< mode="RemoteOnly" defaultredirect="Customerror.aspx"> < statuscode="404" redirect="Notfound.aspx"> < /customErrors >'This will take the user to NotFound.aspx defined in IIS.

How do you implement Paging in .Net?
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.

Can you create an app domain?
Yes, We can create user app domain by calling on of the following overload static methods of the System.AppDomain class1. 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 are the various security methods which IIS Provides apart from .NET ?
The various security methods which IIS provides are
a) Authentication Modes
b) IP Address and Domain Name Restriction
c) DNS Lookups DNS Lookups
d) The Network ID and Subnet Mask
e) SSL

Where does the Web page belong in the .NET Framework class hierarchy?
System.Web.UI.Page

Where do you store the information about the user’s locale?
System.Web.UI.Page.Culture

Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
· 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.

Other ASP.Net related interview questions are available at

Set 1 of ASP.Net Interview questions or Asp.Net FAQs
Set 2 of ASP.Net Interview questions or Asp.Net FAQs

New features of C# 4.0 is available at C# 4.0 FAQs or C# 4.0

Basic .Net questions are available at .Net Frame works FAQ or .Net interview question