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C# Extension Methods


Extension Methods in C#


Extension methods allow you to add methods to an existing type without changing then existing type or creating a new derived type.


The most common extension method in the LINQ operators added to the existing System.Collections.IEnumerable types.


To use standard query operators for most of the <IEnumerable> types add the using directive in your file,


using System.Linq;  (You may also need to add a reference to System.Core.dll)

class ExtensionMethods2

{

      static void Main()

     {

           int[] ints = { 10, 45, 15, 39, 21, 26 };

           var result = ints.OrderBy(g => g); 

           foreach (var i in result) { System.Console.Write(i + " "); }

     }

}

//Output: 10 15 21 26 39 45


Extension methods are created as non-generic static methods but called by instance method syntax.


namespace ExtensionMethods

{

    public static class MyExtensions

    {

           public static int WordCount(this String str)

          {

                return str.Split(new char[] { ' ', '.', '?' }, StringSplitOptions.RemoveEmptyEntries).Length;

          }

    }

}


The WordCount extension method defined for System.String class can be called in the application as below,


using ExtensionMethods;

string s = "This is a string";

int count = s.WordCount();


Note -  When creating extension methods for a type, if the signature is the same as the method in the type then it won't be invoked.






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