Implement and Call a Custom Extension Method

Implement and Call a Custom Extension Method

Author Kaden Kang 康翌

2009-5-14

How to Implement a Custom Extension Method

1.        Define a static class to contain the extension method.

2.        Create a static Method.

3.        Using this keyword to extension method.

Method Extension means developer can add some new method to existent CLR type open rules, not to generate sub class or recompile previous type.

The following code shows how to implement a custom extension method.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

 

namespace MyExtensionMethod

{

    /// <summary>

    /// Note: the class must have the static keyword

    /// </summary>

    public static class MyExtensionMethod

    {

        /// <summary>

        /// Extension method define

        /// </summary>

        /// <param name="str">string instance</param>

        /// <returns>string</returns>

        public static string MyString(this string str)

        {

            return str + " Kaden Kang";

        }

    }

}

Note: “This” means “string” type extension.

How to Call a Custom extension Method

The following code shows how to call a custom extension method.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using MyExtensionMethod;

 

namespace ExtensionMethodTest

{

    class Program

    {

        static void Main(string[] args)

        {

            string str = "test";

            Console.WriteLine(str.MyString());

        }

    }

}

Reference

http://msdn.microsoft.com/en-us/library/bb311042.aspx