ref参数

能够将一个变量带入一个方法中进行改变，改变完成后，再讲改变后的值带出方法。
ref参数要求在方法外必须为其赋值，而方法内可以不赋值。

 class Program    {        static void Main(string[] args)        {            double salary = 5000;            JiangJin(ref salary);            Console.WriteLine(salary);            Console.ReadKey();        }        public static void JiangJin(ref double s)        {            s += 500;        }        public static void FaKuan(double s)        {            s -= 500;        }    }

 class Program    {        static void Main(string[] args)        {            //使用方法来交换两个int类型的变量            int n1 = 10;            int n2 = 20;            //int temp = n1;            //n1 = n2;            //n2 = temp;            Test(ref n1, ref  n2);            Console.WriteLine(n1);            Console.WriteLine(n2);            Console.ReadKey();            //n1 = n1 - n2;//-10 20            //n2 = n1 + n2;//-10 10            //n1 = n2 - n1;//20 10        }        public static void Test(ref int n1, ref  int n2)        {            int temp = n1;            n1 = n2;            n2 = temp;        }    }