ref的用法

ref可以修改变量作为参数调用的值，但必须要初始化，不能在调用的函数中初始化

static void Main(string[] args)
        {
            int myNumber = 5;
            Console.WriteLine("myNumber = {0}.", myNumber);
            ShowDouble(ref myNumber);
            Console.WriteLine("myNumber = {0}.", myNumber);
            Console.ReadKey();
        }
        static void ShowDouble(ref int var)
        {
            var *=2 ;
            Console.WriteLine("val doubled = {0}.", var);
            return; 
        }
输出：
mynumber = 5; val doubled = 10; myNumber = 10.

非法：

const int myNumber = 5;
Console.WriteLine("myNumber = {0}.", myNumber);
ShowDouble(ref myNumber);
Console.WriteLine("myNumber = {0}.", myNumber);
Console.ReadKey();

非法：

int myNumber;
ShowDouble(ref myNumber);
Console.WriteLine("myNumber = {0}.", myNumber);
Console.ReadKey();