using System;

public class Program

{

    public static void Main()

    {

        var drink1 = new Drink() { Tea = 3};

        var drink2 = new Drink() { Tea = 27};

        Console.Write(drink1.Tea + ", " + drink2.Tea);

        Console.WriteLine("  --> 原資料");

        // Swap 方法

        Drink.Swap(drink1, drink2);

        Console.Write(drink1.Tea + ", " + drink2.Tea);

        Console.WriteLine("  --> 呼叫Swap後");

        // 呼叫 Swap 方法等同如下， swap方法內部的區域變數命名不同，但指向同一個物件

        // 換句話說，記憶體裡還是只有 drink1, drink2 兩個 object，並無新增

        // 方法內部的drink1, drink2指向外部傳入的object

        var drink1a = drink1;

        var drink2a = drink2;

        var temp = drink1a;

        drink1a = drink2a;

        drink2a = temp;

        Console.Write(drink1.Tea + ", " + drink2.Tea);

        Console.WriteLine("  --> 等同呼叫Swap的代碼 ");

        // Swap by ref 方法

        Drink.SwapByRef(ref drink1, ref drink2);

        Console.Write(drink1.Tea + ", " + drink2.Tea);

        Console.WriteLine("  --> 呼叫SwapRef");

        // by ref 方法等同如下，一樣是傳遞 reference

        // 只是方法內部的 指向原外部的變數命名

        var tmp3 = drink1;

        drink1 = drink2;

        drink2 = tmp3;

        Console.Write(drink1.Tea + ", " + drink2.Tea);

        Console.WriteLine("  --> 等同呼叫SwapRef的代碼");

        // 傳值 != 傳指標 != 傳參考

        // pass by value

        // pass by pointer

        // pass by reference

        // 交換新寫法 XDDD

        Console.WriteLine("\n加碼新語法：");

        (drink1, drink2) = (drink2, drink1);

        Console.WriteLine(drink1.Tea + ", " + drink2.Tea);

        // method內有參考型別的參數，是以傳指標方式傳值（創造新區域變數，複製呼叫方變數記憶體位置）

        // method內有參考型別的ref參數，則以傳參考方式傳值（無創造域變數，以參考方式直接操作呼叫方變數）

    }

​

    public class Drink

    {

        public int Tea;

        public static void Swap(Drink drink1, Drink drink2)

        {

            Drink temp = drink1;

            drink1 = drink2;

            drink2 = temp;

        }

        public static void SwapByRef(ref Drink drink1, ref Drink drink2)

        {

            Drink temp = drink1;

            drink1 = drink2;

            drink2 = temp;

        }

    }                         

}