使用 ref 关键字通过引用传递

文档

在 C#中,可以通过值或引用将参数传递给参数。通过引用传递使函数成员,方法,属性,索引器,运算符和构造函数能够更改参数的值,并使更改在调用环境中保持不变。要通过引用传递参数,请使用 refout 关键字。

refout 之间的区别在于 out 意味着必须在函数结束之前分配传递的参数。在 ref 传递的对比度参数可以改变或保持不变。

using System;

class Program
{
    static void Main(string[] args)
    {
        int a = 20;
        Console.WriteLine("Inside Main - Before Callee: a = {0}", a);
        Callee(a);
        Console.WriteLine("Inside Main - After Callee: a = {0}", a);
        
        Console.WriteLine("Inside Main - Before CalleeRef: a = {0}", a);
        CalleeRef(ref a);
        Console.WriteLine("Inside Main - After CalleeRef: a = {0}", a);
     
        Console.WriteLine("Inside Main - Before CalleeOut: a = {0}", a);
        CalleeOut(out a);
        Console.WriteLine("Inside Main - After CalleeOut: a = {0}", a);
        
        Console.ReadLine();
    }

    static void Callee(int a)
    {
        a = 5;
        Console.WriteLine("Inside Callee a : {0}", a);
    }

    static void CalleeRef(ref int a)
    {
        a = 6;
        Console.WriteLine("Inside CalleeRef a : {0}", a);
    }
    
    static void CalleeOut(out int a)
    {
        a = 7;
        Console.WriteLine("Inside CalleeOut a : {0}", a);
    }
}

输出

Inside Main - Before Callee: a = 20
Inside Callee a : 5
Inside Main - After Callee: a = 20
Inside Main - Before CalleeRef: a = 20
Inside CalleeRef a : 6
Inside Main - After CalleeRef: a = 6
Inside Main - Before CalleeOut: a = 6
Inside CalleeOut a : 7
Inside Main - After CalleeOut: a = 7