Lu: 物件的垃圾收集機制

當一個物件不再具有任何參考，物件就會被垃圾收集機制處理掉。

建立具有Elephant類別的程式，產生兩個Elephant實例，接著讓它們交換參考，不要讓任何Elephant實例被垃圾收集機制處理掉。

主程式

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace Swap
{
   public partial class Form1 : Form
   {
   Elephant lucinda;
   Elephant lloyd;
   Elephant change;

   public Form1()
   {
   InitializeComponent();

   lucinda = new Elephant(); ←初始化
   lucinda.Name = "Lucinda";
   lucinda.EarSize = 33;

   lloyd = new Elephant(); ←初始化
   lloyd.Name = "Lloyd";
   lloyd.EarSize = 40;

   }

   private void button1_Click(object sender, EventArgs e)
   {
   lloyd.WhoAmI();
   }

   private void button2_Click(object sender, EventArgs e)
   {
   lucinda.WhoAmI();
   }

   private void button3_Click(object sender, EventArgs e)
   {
   change = lloyd;←兩個物件裡的參考要交換需要有第三個參考來幫忙，以避免其中一個物件因為裡面不再有參考而被當作垃圾收集處理掉。
   lloyd = lucinda;
   lucinda = change;
   MessageBox.Show("Objects swapped");
   }

   }
}

Elephant類別程式

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;

namespace Swap
{
   class Elephant
   {
   public int EarSize;
   public string Name;

   public void WhoAmI()
   {
   MessageBox.Show("My EarSize are " + EarSize + " inches tall.", Name + " say...");
   }
   }
}

Demo圖