C#的扩展方法

using System;

using System.Collections;

using System.Collections.Generic;

using System.IO;

using System.Reflection;

using System.Text.RegularExpressions;

using System.Linq;

namespace codeTest

{

    class Program

    {

        static void Main(string[] args)

        {

            string str = "12312312 123123 123123";

            Console.WriteLine(str.WordCount());

            MyClass mylClass = new MyClass() { str = "" };

            Console.WriteLine(mylClass.WordCount());

            Console.ReadLine();

        }

    }

    /// <summary>

    /// 扩展方法必须在静态类里面，扩展方法也必须是静态的，首参数为this

    /// </summary>

    public static class stringExtension

    {

        public static int WordCount(this string str)

        {

            return str.Count();

        }

        public static int WordCount(this MyClass mylClass)

        {

            return mylClass.str.Count();

        }

    }

    public class MyClass

    {

        public string str;

    }

}