使用 ref 關鍵字通過引用傳遞

從文件 ：

在 C#中，可以通過值或引用將引數傳遞給引數。通過引用傳遞使函式成員，方法，屬性，索引器，運算子和建構函式能夠更改引數的值，並使更改在呼叫環境中保持不變。要通過引用傳遞引數，請使用 ref 或 out 關鍵字。

ref 和 out 之間的區別在於 out 意味著必須在函式結束之前分配傳遞的引數。在 ref 傳遞的對比度引數可以改變或保持不變。

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);
    }
}

輸出 ：

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