C#-Constructors,Static Constructors and Destructors Execution in Inheritance

While taking interview for .NET Technologies i often ask about the execution sequence of the constructor and destructor in inheritance But from the my experience i have found that lots of people are still confused with execution sequence of constructor and destructors. Lets create a simple example and learn some basic things that is very important while using inheritance in C#.

• Constructors will be executed in from parent to child sequence means first parent class constructor will be executed then after that child class constructor will be executed.
• Destructors execution order is reverse then constructors first it will execute child class destructor and then it will execute the parent class destructor.
• Static constructors are different then the normal constructors and its executes when first object of class is created it will be executed. Most of people are very confused this kind of scenario in inheritance. Here scenario will be like when the first object of child class created then it will execute the child class static constructor and then after the parent class static constructor is executed. After that it will never got executed.

Lets create a simple class which will illustrate the above worlds. First lets create a class A with constructor,destructor and a static constructor.

public class A
 {
     static A()
     {
         System.Console.WriteLine("A Static Constructor");
     }
     public A()
     {
         System.Console.WriteLine("A public constructor");
     }

     ~A()
     {
         System.Console.WriteLine("A Destructor");
     }
 }

Now we will inherit this class with the another class B which is also having constructor,destructor and a static constructor.

public class B : A
 {
     static B()
     {
         System.Console.WriteLine("B Static Constructor");
     }
     public B()
     {
         System.Console.WriteLine("B public constructor");
     }

     ~B()
     {
         System.Console.WriteLine("B Destructor");
     }
 }

Now lets create two objects of Class B in main function of our console application to see how constructors works and after that we will destroy the object via assigning null values and then forcefully we will do Garbage Collection via GC.Collect() to see how destructors works below is the code for that.

 class Program
 {
     static void Main(string[] args)
     {
         B b1 = new B();
         B b2 = new B();
         //code return to destroy object of a class
         b1=b2 = null;
         GC.Collect();
         Console.ReadLine();

     }
 }

After running the console application output will be as follows.

As you can see static constructors are only executed when the first object of a class is created and Constructors are executed like parent to child way and in reverse destructors are executed from child to parent way. Hope this will help you understand execution sequence of constructor in inheritance.

Technorati Tags: Constructors,Destructors,Static Constructor,C#.NET

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Singleton Class in C#

Singleton pattern is very popular pattern used by programmer. The idea behind the singleton pattern is to have only one instance of a class at any time. This kind of pattern is very useful for for heavy resources like Linq Data Context etc. It is also useful in multithreaded application where different thread of application try to crate instance of one class but it should be thread safe. It can be also useful for global resources and state objects. In singleton class there are two things required. One static variable which hold the instance of class and other is a static method which will return the instance of singleton class. Here is the example of singleton class

 public class MySingleTon
  {
      private static MySingleTon mySingleTonInstance = new MySingleTon();

      private MySingleTon()
      {
          //private constructor
      }
      public static MySingleTon  GetInstace()
      {
          return mySingleTonInstance;
      }

  }

Now we are done with calling single ton class like following.

 MySingleTon objSingleTon = MySingleTon.GetInstace(); 

The above example is not thread safe so it may be possible that different thread can create different instance of classes. To make above singleton class thread safe we need to change code like following.

   public class MySingleTon
  {
      private static MySingleTon mySingleTonInstance = new MySingleTon();

      private MySingleTon()
      {
          //private constructor
      }
      public static MySingleTon  GetInstace()
      {
          lock (typeof(MySingleTon))
          {
              if (mySingleTonInstance == null)
              {
                  mySingleTonInstance = new MySingleTon();
              }
              return mySingleTonInstance;
          }
       
      }
   }

Hope this will help you…

Technorati Tags: Singleton Pattern,SingleTon Class in C#

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Visual Studio 2010-Automatically Adjust Visual Experience.

Visual studio 2010 is great IDE and i am discovering everyday some thing new. Today i have discovered one of fantastic option to increase performance of your visual studio IDE. Visual Studio 2010 has option when we enabled it it will automatically adjust the visual and client experience as per your hardware configuration. It will increase the performance of visual studio and productivity in lower hardware also. You can find that checkbox under Tools->General-> Automatically adjust visual experience based on client performance. There are two checkbox is given one for above and another for Rich User Experience but they may decrease your visual studio performance. Like following.

Technorati Tags: Visual Web Developer 2010,Visual Studio 2010,UserExperience

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Indexer class in C#

While taking interviews for Microsoft.NET i often ask about indexer classes in C#.NET and i found that most of people are unable to give answer that how we can create a indexer class in C#.NET. We know the array in C#.NET and each element in array can be accessed by index same way for indexer class a object was class can be accessed by index. Its very easy to create a indexer class in C#. First lets looks some points related to indexer class in C#.

• Indexer class object can be accessed by index only.
• We can use same mechanism to access object of indexer class as we are doing it for array.
• You can can specify any valid C# type as return type of indexer classes.
• You must have to create a property with parameter using this keyword for indexer class.
• You can also implement multi parameter indexer also.

Let’s create simple indexer class with single parameter and for string type.

 public class MyIndexer
 {
     private string[] MyIndexerData;
     private int SizeOfIndexer;

     //declaring cursor to assing size of indexer
     public MyIndexer(int sizeOfIndex)
     {
         this.SizeOfIndexer = sizeOfIndex;
         MyIndexerData = new string[SizeOfIndexer];
     }

     public string this[int Position]
     {
         get
         {
             return MyIndexerData[Position];
         }
         set
         {
             MyIndexerData[Position] = value;
         }
     }
}

Now we done with indexer class and lets create object of that indexer class and will see output of our console application also. Following is the code for that.

namespace ConsoleApplication1
{
 class Program
 {
     static void Main(string[] args)
     {
         int indexSize=5;
         MyIndexer objMyIndexer = new MyIndexer(indexSize);
         for (int i = 0; i < indexSize; i++)
         {
             objMyIndexer[i] = i.ToString();
             Console.WriteLine("Indexer Object Value-[{0}]: {1}",
         i, objMyIndexer[i]);
         }
         Console.ReadKey();
     }
 }
}

and Here is the output for the indexer class console application.

Technorati Tags: Indexer,C#,Array

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Microsoft.NET 4.0/VB.NET 10 Automatic Properties

In C# we are having automatic properties since C# 3.5 framework but now with Microsoft.NET 4.0 Framework VB.NET 10.0 version we are also having automatic properties for VB.NET Also.

Like in C# we can define automatic like following.

Public string TestProperty
{
get;
set;
}

Same way we can define in automatic Property in VB.NET as follows.

Public Property TestProperty As String 

You can use this properties any where in class same as C# automatic property.

Technorati Tags: VB.NET 10,Automatic Properties.

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ASP.NET and Load balancing.

In one of our project the site usage of site was very heavy and we need to migrate it to load balancing server. I have never configured the sites in the load balancing server but it was quite interspersing experience Here are the some points which we need to take care while we move asp.net sites into the load balancing environments. So first we will see what is load balancing.

Following is a load balancing definition from the Google.

In computer networking, load balancing is a technique to distribute workload evenly across two or more computers, network links, CPUs, hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, minimize response time, and avoid overload.

Following are the points which you need to take care when you are deploying your asp.net sites into load balancing server environments.

Machine Key Should be same for both servers: View state and session both are depends on the machine key. If you machine key is not same then you will have problems related to session and view state you may loose your session and view state in between request during post backs. If machine key will not be same then its possible that you can get strange result in Ajax requests. There is a machine key section in web.config where you can specify machine key.

<machineKey validationKey='C44B8B7C521CB5BC7E602BAE6118AA44CD690C7304817129DA27C17E800132A1BD946C6D9AD12F0A5B342840C7D130564195428160B7466146938CA9E3A62686'   decryptionKey='0E9DF2DA7F210B84087690FF0BF25C905182AD81E16A5FA9'   validation='SHA1'/>

Session Configuration: Any web application is not possible without having session as web pages are stateless so you can configure session in load balancing also. There are two configuration which can be used in load balancing environments. One is state service and another is Storing session in SQL Server.

Following is a good link to learn how you can configure sessions state in asp.net application.

http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/0d9dc063-dc1a-46be-8e84-f05dbb402221.mspx?mfr=true

And here is a good link to configure session on SQL Server.

http://support.microsoft.com/kb/317604

You can configure session state mode in your web.config like following.

<sessionState mode="SQLServer" StateConnectionString="tcpip=127.0.0.1:42424"

SqlConnectionString = "data source=SERVERNAME; user id=sa; password=sa"

cookieless="false" timeout="20" />

enableViewStateMac="false": This is a alternative approach to machine key. This will tell asp.net engine that whether it should check Machine authentication check or not and if you made it false then it will not check for machine authentication. You can define that in your web.config pages section like following.

<system.web>
<pages enableViewStateMac="false" />
</system.web>

Caspol Utility: You can use caspol utility to share some resources on between load balancing servers. Like we have file base cache dependency in our application so we have created a central location(A shared folder for cache files) for the both the server and used Caspol utility to give full trust share on that folder for load balancing servers. Following are some of the good links to which will teach how you can use CasPol utility to for asp.net application

http://blogs.msdn.com/shawnfa/archive/2004/12/30/344554.aspx

http://forums.asp.net/p/1119925/1881331.aspx#1881331

http://www.eggheadcafe.com/software/aspnet/30227544/caspol-addfulltrust.aspx

File Replication:File Replication is also an important features of load balancing you should have replication enabled on the folders of web application so if you upload anything on one server it should replicated to other sites. Following is good link to understand file replication.

http://www.tgrmn.com/web/kb/item28.htm

Sticky Sessions: In some scenario Sticky session is very useful. In one page our application we have used extensive Ajax and we need that for each request and partial post back it should stay on one server till request completes.To achieve that we can used sticky session. Following are some good links to know about sticky sessions.

http://dev.fyicenter.com/Interview-Questions/JavaScript/What_does_the_term_sticky_session_mean_in_a_web_.html

http://blogs.msdn.com/drnick/archive/2007/07/13/sticky-sessions.aspx

Hope this will help you on deploying your asp.net on load balancing sites. Following are some good links for understanding load balancing in more details

http://technet.microsoft.com/en-us/library/bb742455.aspx
http://support.microsoft.com/kb/323437
http://technet.microsoft.com/en-us/library/cc754833%28WS.10%29.aspx.
http://edge.technet.com/Media/Network-Load-Balancing-NLB-in-Windows-Server-2008/

Technorati Tags: ASP.NET & Load Balancing,ASP.NET,NLB,Load Balancing.

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Rename feature in Visual Web Developer 2010/Visual Studio 2010

Visual web developer is great tool and I am playing more and more with it and every time I am discovering some new features of it. Recently I have discovered a very cool feature of it. I want to rename a variable in visual studio 2010 Web Developer express edition and I found a great refractor tool for that which will rename that variable in all the instance and all the methods. First you need to select variable which you want to rename and then you need to Right Click ->Refractor->Rename. You can also invoke that via its shortcut Ctrl + R,Ctrl +R and it will be available For reference see the below screenshot.

Once you click the rename which will have a dialog box open which will ask for new name or variable like following.

It is also having options for search in comments and search in string. Search in comment will search and replace in comment and search in string will replace word for any string which contains that variable name. Once you put new name in dialog box it will display a preview of replaced strings like following. Here also you can select where you need to rename and where you don’t want to rename and this is really cool. :)

Technorati Tags: Rename,VisualStudio2010,Visual Web Developer 2010

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