入门示例: 假如有一个label,我们希望像走马灯一样,从1显示到100
private void button1_Click(object sender, EventArgs e) { for (int i = 0; i <= 100; i++) { label1.Text = i.ToString(); } }
但这种写法,只会卡一下,然后label显示100,没有变化的. 如果用doEvents,就可以变化了
private void button1_Click(object sender, EventArgs e) { for (int i = 0; i <= 100; i++) { label1.Text = i.ToString(); Thread.Sleep(50); Application.DoEvents(); } }
但是stackoverflow里说Application.DoEvents是为了适应vb项目迁移而设的,尽量不推荐使用
改成多线程,子线程是不能直接修改UI上的控件的,只能通过委托,让UI线程来修改.
delegate void D(object obj); private void button2_Click(object sender, EventArgs e) { for (int i = 0; i < 10; i++) { Thread t = new Thread(new ParameterizedThreadStart(SetTextBoxValue)); t.IsBackground = true; t.Start(i.ToString()); Debug.WriteLine("Thread #"+ i +" Start"); } } void SetTextBoxValue(object obj) { if (label1.InvokeRequired) { Debug.WriteLine("Thread #" + obj + "InvokeRequired,set Delegate"); D d = new D(SetTextBoxValue); label1.Invoke(d, obj); //异步的话,不保证哪个线程先完成.最后的结果是8或9 } else { Debug.WriteLine("Thread #" + obj + " UI Change ");//An unhandled exception of type ‘System.InvalidOperationException‘ occurred in System.Windows.Forms.dll //Additional information: 线程间操作无效: 从不是创建控件“label1”的线程访问它。 this.label1.Text = obj.ToString(); Thread.Sleep(50); } }
debug的输出如下: 启动10个线程.10个线程把修改控件属性的操作交给委托, 最后再UpdateUI
Thread #0 Start Thread #0InvokeRequired,set Delegate The thread 0x19ec has exited with code 259 (0x103). Thread #1 Start Thread #1InvokeRequired,set Delegate The thread 0x570 has exited with code 259 (0x103). Thread #2 Start Thread #2InvokeRequired,set Delegate The thread 0x1d04 has exited with code 259 (0x103). Thread #3 Start Thread #4 Start Thread #4InvokeRequired,set Delegate The thread 0x1a8c has exited with code 259 (0x103). Thread #5InvokeRequired,set Delegate Thread #3InvokeRequired,set Delegate The thread 0x1a88 has exited with code 259 (0x103). The thread 0xedc has exited with code 259 (0x103). Thread #5 Start Thread #6 Start Thread #7 Start Thread #7InvokeRequired,set Delegate Thread #6InvokeRequired,set Delegate The thread 0x1b58 has exited with code 259 (0x103). The thread 0x694 has exited with code 259 (0x103). Thread #8InvokeRequired,set Delegate The thread 0x1680 has exited with code 259 (0x103). Thread #8 Start Thread #9 Start Thread #0 UI Change Thread #9InvokeRequired,set Delegate The thread 0x177c has exited with code 259 (0x103). Thread #1 UI Change Thread #2 UI Change Thread #4 UI Change Thread #5 UI Change Thread #3 UI Change Thread #7 UI Change Thread #6 UI Change Thread #8 UI Change Thread #9 UI Change The thread 0x67c has exited with code 0 (0x0).
原文：https://www.cnblogs.com/zitjubiz/p/11531679.html