ASP.NET Interview Questions and Answers (3.5)

Asp.net  Interview Questions and Answers (3.5)

What is the Windows Presentation Foundation

Answer :: The Windows Presentation Foundation is the unified presentation subsystem for Windows. It

consists of a display engine and a managed-code framework. The Windows Presentation Foundation unifies

how Windows creates, displays, and manipulates documents, media, and user interface, which enables

developers and designers to create visually-stunning, differentiated user experiences that improve customer

connection. When it ships, scheduled for 2006, the Windows Presentation Foundation will be available on

Windows XP, Windows Server 2003 and all future releases of the Windows operating system. When delivered,

the Windows Presentation Foundation will become Microsoft’s strategic user interface technology. 

What is XAML

Answer :: XAML, Extensible Application Markup Language, is Microsoft’s XML-based language for

creating a rich graphical user interface....XAML was introduced in 2003 as the language behind Windows

Presentation Foundation, then known as Avalon.

What is the Windows Presentation Foundation

Answer :: The Windows Communication Foundation is a set of technologies for building and running connected

systems.

The Windows Communication Foundation is a new breed of communications infrastructure built around the

Web services architecture. Advanced Web services support in the Windows Communication Foundation

provides secure, reliable, and transacted messaging along with interoperability. The Windows Communication

Foundation’s service-oriented programming model is built on the .NET Framework and simplifies

development of connected systems. The Windows Communication Foundation unifies a broad array of

distributed systems capabilities in an extensible architecture, spanning transports, security systems, messaging

patterns, encodings, network topologies and hosting models. The Windows Communication Foundation will be

an integral capability of Windows Vista and will also be supported on Windows XP and Windows Server 2003.

Microsoft has also done significant work to integrate the Windows Communication Foundation with existing

Microsoft technologies for building distributed systems including COM+, MSMQ, and ASP.NET Web services.

Applications built with those existing technologies can now be exposed as services without modification to the

application. This infrastructure-level solution greatly assists developers in exposing existing applications as

services. The Windows Communication Foundation also provides simple and mechanical mechanisms to

migrate applications that use .NET remoting, ASP.NET Web services, and .NET Enterprise Services to natively

use the Windows Communication Foundation programming model. 

Describe the usefulness Visual Studio 2008 Split View feature?

Answer :: Visual Studio allows you to set the default view (Split, Source or Design) and to choose between a

horizontal split and a vertical split. Especially this last option is very handy when you have a widescreen

monitor.

To enable vertical split-view orientation in VS 2008, select the tools->options menu item and go to the HTML

Designer->General section. Then check the "Split views vertically" checkbox:

Can you compare Nested Master Page Support in Visual Studio 2008 as compared to VS 2005?

Answer :: Already Visual Studio 2005 supports nested master pages concept with .NET 2.0, but the problem

with this Visual Studio 2005 that pages based on nested masters can't be edited using WYSIWYG web

designer. But now in VS 2008 you can even edit the nested master pages.

What is a Nested Master Page and how will you use it ?

Answer :: Master pages can be nested, with one master page referencing another as its master. Nested master

pages allow you to create componentized master pages. For example, a large site might contain an overall

master page that defines the look of the site. Different site content partners can then define their own child

master pages that reference the site master and that in turn define the look for that partner's content.

A child master page has the file name extension .master, as with any master page. The child master page

typically contains content controls that are mapped to content placeholders on the parent master page. In this

respect, the child master page is laid out like any content page. However, the child master page also has

content placeholders of its own to display content supplied by its own child pages. The following three page

listings show a simple nested master page configuration.

What is the enhanced ajax support for Asp.net in 3.5 as compared to the previous versions of Asp.net ?

Answer :: Previously developer has to install AJAX control library separately that does not come from VS, but

now if you install Visual Studio 2008, you can built-in AJAX control library. This Ajax Library contains plenty of

rich AJAX controls like Menu, TreeView, webparts and also these components support JSON and VS 2008

contains in built ASP.NET AJAX Control Extenders.

What is VS 2008 Multi-Targeting

Answer :: Earlier you were not able to working with .NET 1.1 applications directly in visual studio 2005. Now in

Visual studio 2008 you are able to create, run, debug the .NET 2.0, .NET 3.0 and .NET 3.5 applications. You

can also deploy .NET 2.0 applications in the machines which contains only .NET 2.0 not .NET 3.x. 

C# interview Questions and Answers

C# interview Questions and Answers :

What is the syntax to inherit from a class in C#?

Place a colon and then the name of the base class. Example: class MyNewClass :

MyBaseClass

Can you prevent your class from being inherited by another class?

Yes. The keyword “sealed” will prevent the class from being inherited.

Can you allow a class to be inherited, but prevent the method from being overridden?

Yes. Just leave the class public and make the method sealed.

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.

When do you absolutely have to declare a class as abstract?

1. When the class itself is inherited from an abstract class, but not all base abstract

methods have been overridden.

2. When at least one of the methods in the class is abstract.

What is an interface class?

Interfaces, like classes, define a set of properties, methods, and events. But unlike classes,

interfaces do not provide implementation. They are implemented by classes, and defined

as separate entities from classes.

Why can’t you specify the accessibility modifier for methods inside the interface?

They all must be public, and are therefore public by default.

Can you inherit multiple interfaces?

Yes. .NET does support multiple interfaces.

What happens if you inherit multiple interfaces and 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. To Do: Investigate

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

System.Object.

What does the term immutable mean?

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.

What’s the difference between System.String and System.Text.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.

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 a string is changed, a new instance in

memory is created.

Can you store multiple data types in System.Array?

No.

What’s the difference between the System.Array.CopyTo() and

System.Array.Clone()?

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.

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

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

What’s the .NET collection class that allows an element to be accessed using a

unique key?

HashTable.

What class is underneath the SortedList class?

A sorted HashTable.

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

Yes.

What’s the C# syntax to catch any possible exception?

A catch block that catches the exception of type System.Exception. You can also omit the

Multi-Threading Concept in c#(Questions and answers)

Multi-Threading Concept in c# (Questions and answers)

Multithreading is the ability of an operating system to concurrently run programs that have been divided into threads.

Multithreading offers better utilization of processors and other system resources.

Example:

A program can spell check and save the data to disk while sending data to be printed. 

Advantages and disadvantages of using multithreading

Advantages:

Simultaneous access to multiple applications

Reduced number of required servers

Improved performance and concurrency

Simplified coding of remote procedure calls and conversations

Disadvantages:

Code writing, debugging, managing concurrency, testing, porting existing code is difficult in multithreading and multicontexting.

Programmers need to remove static variables and replace any code that is not thread-safe to introduce threading into a previously non threaded application. 

Benefits of using the Thread Pool.

The benefits of using a Thread Pool are:

Thread creation and destruction overhead is negated,

Better performance and better system stability.
It is better to use a thread pool in cases where the number of threads is very large. 

Explain how to create and manage threads using Thread class in the System.Threading namespace in .NET.

using System.Threading;

private void ThreadTask()

{

         int x;

         int val;

         Random r=new Random();

         while(true)

         {

             x=this.progressBar1.Step*r.Next(-1,2);

            val = this.progressBar1.Value + x;

            if (val > this.progressBar1.Maximum)

                  val = this.progressBar1.Maximum;

            else if (val < this.progressBar1.Minimum)

                  val = this.progressBar1.Minimum;

            this.progressBar1.Value = val;

            Thread.Sleep(100);

         }

}

You need to write these lines first:

    Thread t1 = new Thread(new ThreadStart(this.ThreadTask));

    t1.IsBackground = true;

    t1.Start(); 

Explain the purpose of Mutex class in .NET.

System uses synchronization mechanism to make sure that a resource is used by only one thread at a time when more than one thread needs to access a shared resource at the same time.

Mutex grants exclusive access to the shared resource to a single thread.

A second thread that needs to acquire a particular mutex is suspended until the first thread releases the mutex. 

Describe the concepts of Monitor class, the interlocked class and the ReaderWriterLock class.

Access to objects by is controlled by the Monitor class. It grants a lock for an object to a single thread.

Critical sections can be access restricted by using object locks.

While a thread owns the lock for an object, no other thread can acquire that lock.

Interlocked class provides atomic operations for variables that are shared by multiple threads.

When two threads are executing concurrently on separate processors error protection is done.

The methods of this class help protect against errors that can occur when the scheduler switches contexts while a thread is updating a variable that can be accessed by other threads.

ReaderWriterLock synchronizes access to a resource. It allows either concurrent read access for multiple threads, or write access for a single thread.

A ReaderWriterLock provides better throughput than a simple one lock a time like Monitor.

Explain about Serialization in .NET. Explain binary serialization and XML serialization

System.Runtime.Serialization namespace provides Serialization in .NET.

The IFormatter interface in the namespace contains Serialize and De-serialize methods that save and load data of a stream.

So we need stream as a container for the serialized object(s) and a formatter that serializes these objects onto the stream to implement serialization in .net.

Binary serialization is a mechanism that creates exact binary copy of the object onto the storage media by writing the data to the output stream such that it can be used to re-construct the object automatically.

XML serialization results in strongly typed classes with public properties and fields that are converted to a serial format for storage or transport. This XML stream conforms to a specific XML Schema definition language (XSD) document.

Explain why Serialization.

An object is stored in a file, a database or even in the memory. However, data to be transferred over a network needs to be in a linear form for which serialization and deserialization are used.

Advantage of serialization is the ability of an object to be serialized into a persistent or a non-persistent storage media and then reconstructing the same object later by de-serializing the object.

Remoting and Web Services depend heavily on Serialization and De-serialization.

Explain the components that comprise the binary serialization architecture.

To binary serialize an object we need a FileStream object,

Constructor: FileStream(file_name, FileMode.Create);

And

BinaryFormatter

Constructor: binaryFormatter.Serialize(fileStreamObject, object1);

What is Formatters? Explain the binary formatter and the SOAP formatter.

A formatter determines the serialization format for objects.

.NET framework provides Binary formatter and SOAP formatter which inherit from the IFormatter interface

The Binary Formatter

It provides binary encoding for compact serialization for storage or socket-based network streams.

It is not appropriate for data to be passed through a firewall.

The SOAP Formatter

It provides formatting that can be used to enable objects to be serialized using the SOAP protocol.

The class is used for serialization through firewalls or diverse systems. 

What are the main advantages of binary serialization?

An object is stored in a file, a database or even in the memory. However, data to be transferred over a network needs to be in a linear form for which serialization and deserialization are used.

Advantage of serialization is the ability of an object to be serialized into a persistent or a non-persistent storage media and then reconstructing the same object later by de-serializing the object.

Also Binary Serialization is faster, supports complex objects too with read only properties and even circular references. 

How do you encapsulate the binary serialization?

public static void SerializeBinary( object o, string file_name)

{

   using (FileStream fs = new FileStream(file_name, FileMode.Create)) {

  BinaryFormatter fmt = new BinaryFormatter ();

  fmt.Serialize(fs, o);

  }

} 

How do you implement a custom serialization?

CUSTOM SERIALIZATION implementation

public class A: ISerializable

{

           private int a;

           protected A(SerializationInfo si, StreamingContext sc)

           {

                   this.a = serializationInfo.GetInt32("a");

           }

           public void ISerializable.GetObjectData(SerializationInfo si, StreamingContext sc)

           {

                     si.AddValue("a", this.a);

            }

} 

What is the difference between the SoapFormatter and the XmlSerializer?

SoapFormatter

SOAP formatter will actually take the field values of an object and store all of that information in the stream passed.

SoapFormatter is better to serialize arbitrary data

XmlSerializer

XML Serialization would just serialize the public properties of an object.

The XML Serializer is used typically for serializing simple types across web services

xmlserializer is better, more flexible and faster 

How can I optimize the serialization process?

The first call to a Web Service takes long because XmlSerializer generate an assembly optimized for each type in memory.

To optimize the serialization process pregeneration of serialization assembly with Visual Studio or sgen.exe is needed.

Implementing serialization separately can also increase the performance. 

Apartments

COM objects in the process as divided into groups called apartments. A COM object lives in exactly one apartment, in the sense that its methods can legally be directly called only by a thread that belongs to that apartment. Any other thread that wants to call the object must go through a proxy.

There are two types of apartments: single-threaded apartments, and multithreaded apartments.

1.Single-threaded Apartments—Single-threaded apartments consist of exactly one thread, so all COM objects that live in a single-threaded apartment can receive method calls only from the one thread that belongs to that apartment. All method calls to a COM object in a single-threaded apartment are synchronized with the windows message queue for the single-threaded apartment's thread. A process with a single thread of execution is simply a special case of this model.

2. Multithreaded Apartments—Multithreaded apartments consist of one or more threads, so all COM objects that live in an multithreaded apartment can receive method calls directly from any of the threads that belong to the multithreaded apartment. Threads in a multithreaded apartment use a model called free-threading. Calls to COM objects in a multithreaded apartment are synchronized by the objects themselves.

Synchronizing objects

Lock

Locks are useful when only one thread at a time can be allowed to modify data or some other controlled resource.

Monitors

Monitors are Like the lock keyword, monitors prevent blocks of code from simultaneous execution by multiple threads. The Enter method allows one and only one thread to proceed into the following statements; all other threads are blocked until the executing thread calls Exit. This is just like using the lock keyword. In fact, the lock keyword is implemented with the Monitor class.

Mutex

A mutex is similar to a monitor; it prevents the simultaneous execution of a block of code by more than one thread at a time. In fact, the name "mutex" is a shortened form of the term "mutually exclusive." Unlike monitors, however, a mutex can be used to synchronize threads across processes.

Semaphore is same as Mutex but it ensures not more than a specified number of threads can access a resource, or section of code.