using System;
namespace ConsoleApplication2
{
    class Program
    {
        public static void AddOne(string a)
        {
           a+="abc";
        }
        public static void AddOne1(ref string a)
        {
            a += "abc";
        }
        static void Main(string[] args)
        {
            string str = "123";
            AddOne(str);
            Console.WriteLine(str);
            AddOne1(ref str);
            Console.WriteLine(str);
            Console.ReadLine();
        }
    }
}
两个输出结果居然不一样！！！这是为什么啊！！！请大家看看哦。