C#中ref参数与out参数的区别

先贴代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Ref_and_Out_test
{
    class Program
    {
        static void Main(string[] args)
        {
            int a =0;        //若不初始化b会产生编译时错误。使用未初始化变量
            int b = 1;      //即使不初始化b也没有问题；
            RefAndOut(ref a,out b);
            Console.WriteLine("after RefAndOut method process");
            Console.WriteLine("a={0},b={1}", a, b);
        }
        static void RefAndOut(ref int a,out int b)
        {
            //b = 1;             //若此处不进行初始化，则try to print b这个语句无法执行
            Console.WriteLine("before change ref a=0 and out b =1 value");
            //try to print b:Console.WriteLine("a={0},b={1}", a, b);
            Console.WriteLine("Now change the value,a to 123 ,b to 999");
            a = 123;
           b = 999;        //若在方法内不对b赋值，则会出现编译时错误提醒必须对b赋值
        &