扩展方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            String s = "aaaa";
            Console.WriteLine(s.extendMethod(true));
            Console.WriteLine(ExtendClass.extendMethod(s, false));
            Console.Read();
        }
    }

    static class ExtendClass
    {
        public static string extendMethod(this string s,bool isLong)
        {
            if (isLong)
                return "Long";
            else
                return "Short";
        }
    }
}