Partial Types, Class and Method in C#.NET 3.0/2.0

With C# 2.0 Microsoft has added partial keyword in C#. So what is partial keyword used for. Lets go through the partial keyword in greater detail.

First and foremost use of the partial keyword is the you can declare one class or method with more then one declaration and at the compilation time it will have one complete class.So now you can declare a class more then one file at the compile time it will be treated as one class.

For example this is one class

//first file Patial Class
public class partial PartialClass
{
   public void First()
   {
     //First function
   }
}

 Here is the another class

public class partial PartialClass
{
   public void Second()
   {
      // Logic...
   }
}

Now at the compile time it will be treat as single class like following.

public class PartialClass
{
   public void First()
   {
      // Logic...
   }
   public void Second()
   {
      // Logic...
   }
}

Same way you can use partial method it will treated as one method as compile time. Partial method will only available with C# 3.0. It will not be available to C# 2.0.

Practical Usage Of Partial Class:

There are lots of way where partial class is useful like many developer can work on same class via creating different files. There are lost of code generators available in market so you can extend the class functionality via marking them partial. Partial class can also be used for the manage code in separate files instead of creating large files. With C# 3.5 linq to sql designer uses this concept to split custom behaviors outside mapping class.

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