Form1.cs
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks; using System.Windows.Forms; namespace WinLock { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void btn_Start_Click(object sender, EventArgs e) { listBox1.Items.Clear(); Thread[] threads = new Thread[10];//使用new關鍵字在堆里創建對象,其生命期相當於全局變量,但訪問的時候與普通變量一樣 Account acc = new Account(1000, this); for (int i = 0; i < 10; i++) { Thread t = new Thread(acc.DoTransactions); t.Name = "線程" + i; threads[i] = t; } for (int i = 0; i < 10; i++) { threads[i].Start(); } } delegate void AddListBoxItemDelegate(string str);//在類的內部也能聲明代理 public void AddListBoxItem(string str) { if (listBox1.InvokeRequired)//如果是跨線程訪問控件則為true { AddListBoxItemDelegate d = AddListBoxItem;//代理 listBox1.Invoke(d, str);//調用代理函數並傳遞參數 } else { listBox1.Items.Add(str);//不是跨線程訪問控件則直接訪問該控件 } } } }
account.cs
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks; namespace WinLock { public class Account { private Object lockedObj = new Object(); int balance; Random r = new Random(); Form1 form1; public Account(int initial, Form1 form1) { this.form1 = form1; this.balance = initial; } /// <summary> /// 取款 /// </summary> /// <param name="amount">取款金額</param> /// <returns>余額</returns> private int Withdraw(int amount) { if (balance < 0) { form1.AddListBoxItem("余額:" + balance + " 已經為負值了,還想取呵!"); } //將lock (lockedObj)這句注釋掉,看看會發生什么情況 lock (lockedObj) { if (balance >= amount) { string str = Thread.CurrentThread.Name + "取款---"; str += string.Format("取款前余額:{0,-6}取款:{1,-6}", balance, amount); balance = balance - amount; str += "取款后余額:" + balance; form1.AddListBoxItem(str); return amount; } else { return 0; } } } /// <summary>自動取款</summary> public void DoTransactions()//Transaction--事務 { for (int i = 0; i < 100; i++) { Withdraw(r.Next(1, 100)); } } } }
不加lock 會出現統一資源被多次利用的情況