C#关键字ref和out

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

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            int a=0;
            //ref传参时必须赋值,但方法体内可不不赋值
            RefMethod(ref a);
            Console.WriteLine(a);
            //out传参时可以不赋值,但方法体内必须赋值
            OutMethod(out a);
            Console.WriteLine(a);
        }

        static void RefMethod(ref int a)
        {
            a = 20;
        }

        static void OutMethod(out int a)
        {
            a = 30;
        }
    }
}