目录
三、Delegate对象的Invoke/BeginInvoke/EndInvoke
1.4、通过Delegate对象.BeginInvoke()将“耗时操作”放在子线程中运行
四、Control的Invoke/BeginInvoke/EndInvoke
1.3、Control.BeginInvoke(Delegate)
一、前言
此文章是我阅读了许多前人的文章、博客后，根据自己的理解做的总结、记录。有不正确的地方望各位多加指正，有侵权的地方望各位提醒我添加引用备注出处。
此文章迭代更新中(20221201-1619)。
对C#中的Delegate、Event、Thread、Task，WinForm中的Control有基本了解。
二、背景
当运行一个WinForm窗体时，UI线程（主线程）上运行着一个消息循环，可以理解“消息循环”是一个死循环，每次循环都会从“消息队列”中取出一个“消息”（WinForm窗体中的用户操作，比如鼠标单击/双击/移入/移出操作，键盘输入等），然后处理这个“消息”，体现在WinForm窗体上就是实时地响应了用户的操作。
如果有个[需求1]：要在点击WinForm窗体中的一个Button后，执行一个非常耗时的操作（比如，sleep 10s）。如果直接在主线程中执行这个耗时操作，主线程因为不能进行消息循环导致WinForm窗体看起来卡死，无法响应用户操作。所以，此时应该创建一个子线程，然后将耗时操作放在子线程中执行，此时，会用到Thread、Task，或者Delegate.BeginInvoke()来创建子线程。
如果有个[需求2]：在[需求1]的基础上，“耗时操作”在子线程中执行完后，需要获取“耗时操作”的执行结果。
如果有个[需求3]：在[需求1]、[需求2]的基础上，“耗时操作”在子线程中执行完后，需要刷新WinForm中的某个Control（比如，需要刷新TextBox文本框中的值。此时也可以理解为是[需求2]的一种特殊情况）。如果“刷新操作”也放在子线程中执行，会抛出运行时异常（跨线程访问控件，即控件是在主线程中创建的，但是却在子线程中对控件进行了刷新）。所以，此时应该将“刷新操作”整体封装成一个Delegate，然后通过Control.Invoke(Delegate)、Control.BeginInvoke(Delegate)将“刷新操作”交给主线程执行，就能解决“跨线程访问控件”的运行时异常。
三、Delegate对象的Invoke/BeginInvoke/EndInvoke
1、基于[需求1]
1.1、直接在主线程中运行“耗时操作”
public Form1()
{
InitializeComponent();
Debug.Listeners.Add(new ConsoleTraceListener());
}
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(10000);
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
protected override void WndProc(ref Message m)
{
Debug.WriteLine(m.Msg.ToString());
base.WndProc(ref m);
return;
}
点击Button后，主线程Sleep 10s。此时WinForm看起来卡死，不响应用户在UI中的操作；Console输出的用户在UI中的操作信息看起来也卡住。
当主线程Sleep结束后，WinForm才响应用户在UI中的操作；Console才继续输出主线程Sleep期间用户在UI中的操作信息。
1.2、通过Thread将“耗时操作”放在子线程中运行
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread thread = new Thread(new ThreadStart(SubThreadMethod));
thread.IsBackground = true;
thread.Start();
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
private void SubThreadMethod()
{
Console.WriteLine(string.Format("Begin SubThread ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(10000);
Console.WriteLine(string.Format("End SubThread ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
点击Button后，通过new Thread()创建一个子线程，子线程执行Thread封装的SubThreadMethod，即Sleep 10s；主线程上仍然运行着消息循环。此时WinForm仍然可以响应用户在UI中的操作。
1.3、通过Task将“耗时操作”放在子线程中运行
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Task task = new Task(new Action(SubThreadMethod));
task.Start();
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
private void SubThreadMethod()
{
Console.WriteLine(string.Format("Begin SubThread ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Task.Delay(10000);
Console.WriteLine(string.Format("End SubThread ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
需要将“输出类型”从“Windows应用程序”改为“控制台应用程序”，然后双击生成的exe。
1.4、通过Delegate对象.BeginInvoke()将“耗时操作”放在子线程中运行
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
CalcDel myCalcDel = new CalcDel(ExeMethod);
Console.WriteLine(string.Format("Before BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
myCalcDel.BeginInvoke(null, null);
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
public delegate void CalcDel();
public void ExeMethod()
{
Console.WriteLine(string.Format("Start ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(10000);
Console.WriteLine(string.Format("End ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
点击Button后，通过Delegate对象.BeginInvoke()创建一个子线程，子线程执行Delegate对象封装的ExeMethod，即Sleep 10s；主线程上仍然运行着消息循环。效果看起来等同于[1.2]、[1.3]。
1.5、总结
对比2、3、4发现，Delegate对象.BeginInvoke()实质上是Thread、Task，创建了一个子线程，然后在子线程中运行Delegate对象封装的操作。
了解了Delegate对象.BeginInvoke()后，再详细对比下Delegate对象.BeginInvoke()、Delegate对象.EndInvoke()的若干用法。
2、基于[需求2]
此段内容，参考文章[WinForm二三事（二）异步操作 - 横刀天笑 - 博客园]，并进行完善
2.1、一去不复返
1.3中展示的就是，子线程运行的“耗时操作”结束后，主线程不需要获取任何关于子线程结束的信息。
2.2、去了还要回->轮询
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Func<int> myAction = new Func<int>(ExeMethod);
Console.WriteLine(string.Format("Begin BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
IAsyncResult asynResult = myAction.BeginInvoke(null, null);
Console.WriteLine(string.Format("End BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
DateTime lastTime = DateTime.MinValue;
while (!asynResult.IsCompleted)
{
DateTime curTime = DateTime.Now;
if((curTime - lastTime).TotalSeconds > 2){
Console.WriteLine(string.Format("NotComplete ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
lastTime = curTime;
}
}
Console.WriteLine(string.Format("Complete ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
int result = myAction.EndInvoke(asynResult);
Console.WriteLine(string.Format("End Click result:{0} ThreadId:{1} {2}", result, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
private int ExeMethod()
{
Console.WriteLine(string.Format("Begin ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(10 * 1000);
Console.WriteLine(string.Format("End ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return 25;
}
点击Button后，通过Delegate对象.BeginInvoke()创建一个子线程，子线程执行Delegate对象封装的ExeMethod，即Sleep 10s；主线程上运行着循环，监视子线程是否执行完毕。
如果子线程没有执行完毕，asynResult.IsCompleted始终为false，主线程中的循环一直进行；如果子线程执行完毕，asynResult.IsCompleted变成true，主线程跳出循环。
主线程在此while循环期间，因为主线程没有运行消息循环，所以WinForm看起来卡死，不响应用户在UI中的操作。
主线程、子线程分别在哪些时间段执行，是由调度算法分配的。比如，截图中，Delegate对象.BeginInvoke()语句执行后，并没有立即执行由Delegate对象.BeginInvoke()语句创建的子线程，而是由调度算法决定什么时候执行子线程中的语句：
1、先拥有控制权的主线程执行了一阵子while循环，然后把控制权交给子线程执行ExeMethod；
2、当子线程Sleep后，又将控制权交给主线程执行while循环；
3、主线程执行了一阵子while循环，等子线程Sleep结束后，将控制权交给子线程；
4、子线程执行完毕后，IAsyncResult对象.IsCompleted由false变为true，控制权交给主线程；
5、主线程跳出while循环。
IAsyncResult asynResult = myAction.BeginInvoke(null, null);
while(!asynResult.IsCompleted){}会使执行该语句的当前线程一直循环，直到子线程运行完Delegate对象封装的操作。
2.3、去了还要回->WaitOne
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Func<int> myAction = new Func<int>(ExeMethod);
Console.WriteLine(string.Format("Begin BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
IAsyncResult asynResult = myAction.BeginInvoke(null, null);
Console.WriteLine(string.Format("End BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
if (asynResult.AsyncWaitHandle.WaitOne(5 * 1000, true))
{
Console.WriteLine(string.Format("Begin wait ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
int result = myAction.EndInvoke(asynResult);
Console.WriteLine(string.Format("End wait result:{0} ThreadId:{1} {2}", result, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
}
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
private int ExeMethod()
{
Console.WriteLine(string.Format("Begin ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(10 * 1000);
Console.WriteLine(string.Format("End ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return 25;
}
1、点击Button后，主线程执行到IAsyncResult asynResult = myAction.BeginInvoke(null, null)时，会创建一个子线程跑ExeMethod，不过此时主线程还拥有控制权，所以主线程继续执行到asynResult.AsyncWaitHandle.WaitOne(5 * 1000, true)，接着主线程会阻塞等待5s（因为子线程还没执行完毕，所以WaitOne让主线程阻塞等待），此时主线程的控制权被调度算法收回；
[主线程在此阻塞等待期间，因为主线程没有运行消息循环，所以WinForm看起来卡死，不响应用户在UI中的操作]
2、调度算法将控制权交给子线程，子线程Sleep 10s，此时子线程的控制权被调度算法收回；
3、5s后，主线程结束了阻塞等待，调度算法将控制权交给主线程，主线程跳过if(asynResult.AsyncWaitHandle.WaitOne(5 * 1000, true)){}花括号中的语句（因为子线程还没执行完毕，所以if条件不满足），直接执行if(){}之后的语句，然后主线程结束，主线程的控制权被调度算法收回；
4、又过了5s后，子线程结束了Sleep，调度算法将控制权交给子线程，然后子线程结束，子线程的控制权被调度算法收回。
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Func<int> myAction = new Func<int>(ExeMethod);
Console.WriteLine(string.Format("Begin BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
IAsyncResult asynResult = myAction.BeginInvoke(null, null);
Console.WriteLine(string.Format("End BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
if (asynResult.AsyncWaitHandle.WaitOne(10 * 1000, true))
{
Console.WriteLine(string.Format("Begin wait ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
int result = myAction.EndInvoke(asynResult);
Console.WriteLine(string.Format("End wait result:{0} ThreadId:{1} {2}", result, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
}
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
private int ExeMethod()
{
Console.WriteLine(string.Format("Begin ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(5 * 1000);
Console.WriteLine(string.Format("End ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return 25;
}
1、点击Button后，主线程执行到IAsyncResult asynResult = myAction.BeginInvoke(null, null)时，会创建一个子线程跑ExeMethod，不过此时主线程还拥有控制权，所以主线程继续执行到asynResult.AsyncWaitHandle.WaitOne(10 * 1000, true)，接着主线程会阻塞等待10s（因为子线程还没执行完毕，所以WaitOne让主线程阻塞等待），此时主线程的控制权被调度算法收回；
[主线程在此阻塞等待期间，因为主线程没有运行消息循环，所以WinForm看起来卡死，不响应用户在UI中的操作]
2、调度算法将控制权交给子线程，子线程Sleep 5s，此时子线程的控制权被调度算法收回；
3、5s后，子线程结束了Sleep，调度算法将控制权交给子线程，然后子线程结束，子线程的控制权被调度算法收回；
4、主线程直接结束了阻塞等待（不用再等5s，因为此时子线程已经结束了，WaitOne是最多等ns，而不是必须等ns），调度算法将控制权交给主线程，主线程执行if(asynResult.AsyncWaitHandle.WaitOne(5 * 1000, true)){}花括号中的语句（因为子线程已经执行完毕，所以if条件满足），接着执行if(){}之后的语句，然后主线程结束，主线程的控制权被调度算法收回。
IAsyncResult asynResult = myAction.BeginInvoke(null, null);
asynResult.AsyncWaitHandle.WaitOne(10 * 1000, true);会使执行该语句的当前线程等待最多10s。
2.4、去了还要回->回调
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Func<int> myAction = new Func<int>(ExeMethod);
Console.WriteLine(string.Format("Begin BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
IAsyncResult asynResult = myAction.BeginInvoke(new AsyncCallback((result) =>
{
Console.WriteLine(string.Format("Begin wait ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
int res = myAction.EndInvoke(result);
Console.WriteLine(string.Format("End wait result:{0} ThreadId:{1} {2}", res, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
}), null);
Console.WriteLine(string.Format("End BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
private int ExeMethod()
{
Console.WriteLine(string.Format("Begin ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(10 * 1000);
Console.WriteLine(string.Format("End ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return 25;
} 
第一种写法：用lambda表达式。
1、点击Button后，主线程执行到IAsyncResult asynResult = myAction.BeginInvoke(new AsyncCallback((result) => {}), null)时，会创建一个子线程跑ExeMethod，不过此时主线程还拥有控制权，所以主线程继续执行直到主线程结束，此时主线程的控制权被调度算法收回；
2、调度算法将控制权交给子线程，子线程Sleep 10s，此时子线程的控制权被调度算法收回；
[子线程在Sleep期间，因为主线程有运行消息循环，所以WinForm看起来没有卡死，会时刻响应用户在UI中的操作]
3、10s后，子线程结束了Sleep，调度算法将控制权交给子线程，子线程执行完ExeMethod后，接着执行回调函数(result) => {}，然后子线程结束，此时子线程的控制权被调度算法收回。
ExeMethod_Delegate exeMethod_Delegate = null;
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
exeMethod_Delegate = new ExeMethod_Delegate(ExeMethod);
for (int i = 3; i < 11; i++)
{
Console.WriteLine(string.Format("{0}-Begin BeginInvoke ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
exeMethod_Delegate.BeginInvoke(10 * i, 1000 * i, new AsyncCallback(ExeMethod_Callback), i);
Console.WriteLine(string.Format("{0}-End BeginInvoke ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
}
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
public delegate int ExeMethod_Delegate(int num, int ms);
private int ExeMethod(int num, int ms)
{
int i = num / 10;
Console.WriteLine(string.Format("{0}-Begin ExeMethod ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(ms);
Console.WriteLine(string.Format("{0}-End ExeMethod ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return num * num;
}
private void ExeMethod_Callback(IAsyncResult result)
{
int i = (int)result.AsyncState;
Console.WriteLine(string.Format("{0}-Begin Callback ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
int product = exeMethod_Delegate.EndInvoke(result);
Console.WriteLine(string.Format("{0}-End Callback 结果:{1} ThreadId:{2} {3}", i, product, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}第二种写法：ExeMethod_Delegate exeMethod_Delegate作为类的成员变量，可以在ExeMethod_Callback回调中，直接用到exeMethod_Delegate。
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
ExeMethod_Delegate exeMethod_Delegate = new ExeMethod_Delegate(ExeMethod);
for (int i = 3; i < 11; i++)
{
Console.WriteLine(string.Format("{0}-Begin BeginInvoke ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
//exeMethod_Delegate.BeginInvoke(10 * i, 1000 * i, new AsyncCallback(ExeMethod_Callback), exeMethod_Delegate);
exeMethod_Delegate.BeginInvoke(10 * i, 1000 * i, ExeMethod_Callback, (exeMethod_Delegate, i));
Console.WriteLine(string.Format("{0}-End BeginInvoke ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
}
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
public delegate int ExeMethod_Delegate(int num, int ms);
private int ExeMethod(int num, int ms)
{
int i = num / 10;
Console.WriteLine(string.Format("{0}-Begin ExeMethod ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(ms);
Console.WriteLine(string.Format("{0}-End ExeMethod ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return num * num;
}
private void ExeMethod_Callback(IAsyncResult result)
{
(ExeMethod_Delegate, int) res = ((ExeMethod_Delegate, int))result.AsyncState;
int i = res.Item2;
Console.WriteLine(string.Format("{0}-Begin Callback ThreadId:{1} {2}", i, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
int product = res.Item1.EndInvoke(result);
Console.WriteLine(string.Format("{0}-End Callback 乘积:{1} ThreadId:{2} {3}", i, product, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}Begin Click ThreadId:1 2024/8/2 13:36:00
3-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
3-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
4-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
4-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
5-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
5-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
6-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
6-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
7-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
7-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
8-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
8-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
9-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
9-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
10-Begin BeginInvoke ThreadId:1 2024/8/2 13:36:00
10-End BeginInvoke ThreadId:1 2024/8/2 13:36:00
End Click ThreadId:1 2024/8/2 13:36:00
3-Begin ExeMethod ThreadId:3 2024/8/2 13:36:00
4-Begin ExeMethod ThreadId:6 2024/8/2 13:36:00
8-Begin ExeMethod ThreadId:4 2024/8/2 13:36:00
6-Begin ExeMethod ThreadId:8 2024/8/2 13:36:00
5-Begin ExeMethod ThreadId:7 2024/8/2 13:36:00
10-Begin ExeMethod ThreadId:10 2024/8/2 13:36:00
9-Begin ExeMethod ThreadId:5 2024/8/2 13:36:00
7-Begin ExeMethod ThreadId:11 2024/8/2 13:36:00
3-End ExeMethod ThreadId:3 2024/8/2 13:36:03
3-Begin Callback ThreadId:3 2024/8/2 13:36:03
3-End Callback 乘积:900 ThreadId:3 2024/8/2 13:36:03
4-End ExeMethod ThreadId:6 2024/8/2 13:36:04
4-Begin Callback ThreadId:6 2024/8/2 13:36:04
4-End Callback 乘积:1600 ThreadId:6 2024/8/2 13:36:04
5-End ExeMethod ThreadId:7 2024/8/2 13:36:05
5-Begin Callback ThreadId:7 2024/8/2 13:36:05
5-End Callback 乘积:2500 ThreadId:7 2024/8/2 13:36:05
6-End ExeMethod ThreadId:8 2024/8/2 13:36:06
6-Begin Callback ThreadId:8 2024/8/2 13:36:06
6-End Callback 乘积:3600 ThreadId:8 2024/8/2 13:36:06
7-End ExeMethod ThreadId:11 2024/8/2 13:36:07
7-Begin Callback ThreadId:11 2024/8/2 13:36:07
7-End Callback 乘积:4900 ThreadId:11 2024/8/2 13:36:07
8-End ExeMethod ThreadId:4 2024/8/2 13:36:08
8-Begin Callback ThreadId:4 2024/8/2 13:36:08
8-End Callback 乘积:6400 ThreadId:4 2024/8/2 13:36:08
9-End ExeMethod ThreadId:5 2024/8/2 13:36:09
9-Begin Callback ThreadId:5 2024/8/2 13:36:09
9-End Callback 乘积:8100 ThreadId:5 2024/8/2 13:36:09
10-End ExeMethod ThreadId:10 2024/8/2 13:36:10
10-Begin Callback ThreadId:10 2024/8/2 13:36:10
10-End Callback 乘积:10000 ThreadId:10 2024/8/2 13:36:10
第三种写法：可以将ExeMethod_Delegate委托本身作为参数，传给Delegate.BeginInvoke()函数，然后在ExeMethod_Callback回调中用到该委托。
从Delegate.BeginInvoke()传入的参数、ExeMethod()函数运行完return的结果，都封装在ExeMethod_Callback()回调函数的IAsyncResult输入参数中。前者通过IAsyncResult.AsyncState获取，后者通过Delegate.EndInvoke()获取。
可以看出，ExeMethod函数和ExeMethod_Callback回调，都是在同一个子线程完成的。
了解了Delegate.BeginInvoke()、Delegate.EndInvoke()的若干用法，再对比下Delegate.Invoke()。
3、Delegate.Invoke()
Delegate.Invoke()不会创建子线程，而是直接在当前线程中运行Delegate封装的操作。
四、Control的Invoke/BeginInvoke/EndInvoke
1、基于[需求3]
此段内容，参考文章[浅谈Invoke 和 BegionInvoke的用法 - 大艺术家007 - 博客园]
1.1、禁用“检查是否跨线程访问控件”，这是不安全的做法
[待完善...]
1.2、Control.Invoke(Delegate)
private void button1_Click(object sender, EventArgs e)
{
Console.WriteLine(string.Format("Begin Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread subThread = new Thread(new ThreadStart(SubThreadMethod));
subThread.Start();
Console.WriteLine(string.Format("End subThread.Start() ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
string a = "";
for (int i = 0; i < 5; i++)
{
a = a + "A";
Console.WriteLine(string.Format("+{0}-Loop-{1} ThreadId:{2} {3}", i, a, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(2000);
}
Console.WriteLine(string.Format("End Click ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
private void SubThreadMethod()
{
Console.WriteLine(string.Format("Begin SubThreadMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
button1.Invoke(new CalcDel(ExeMethod));
//button1.BeginInvoke(new CalcDel(ExeMethod));
Console.WriteLine(string.Format("End BeginInvoke ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
string b = "";
for (int i = 0; i < 7; i++)
{
b = b + "B";
Console.WriteLine(string.Format("={0}-Loop-{1} ThreadId:{2} {3}", i, b, Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
Thread.Sleep(1300);
}
Console.WriteLine(string.Format("End SubThreadMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
public delegate void CalcDel();
private void ExeMethod()
{
Console.WriteLine(string.Format("Begin ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
this.textBox1.Text = DateTime.Now.ToString();
Console.WriteLine(string.Format("End ExeMethod ThreadId:{0} {1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString()));
return;
}
在子线程中运行Control.Invoke(Delegate)，子线程会被阻塞，子线程会等待主线程运行完Delegate封装的操作后，才可继续执行子线程。但是并不意味着，主线程会立即运行Delegate封装的操作。事实上，Delegate封装的操作被放到了主线程的待执行任务队列的末尾。
此时，控制权会立即从子线程交给主线程，只有当主线程运行完Delegate封装的操作后，才会再接着运行子线程中Control.Invoke(Delegate)语句后面的操作；而在主线程运行完Delegate封装的操作之前，子线程（Control.Invoke(Delegate)语句后面的操作）会被阻塞。
1.3、Control.BeginInvoke(Delegate)
在子线程中运行Control.BeginBeginInvoke(Delegate)，也会将Delegate封装的操作交给主线程运行。
此时，子线程（Control.Invoke(Delegate)语句后面的操作）不会被阻塞。至于主线程、子线程的执行顺序，是由调度算法控制的，在用户看来是不确定的。
1.4、Control.InvokeRequired
private void Form1_Load(object sender, EventArgs e)
{
Thread subThread = new Thread(CrossThreadFlush);
subThread.IsBackground = true;
subThread.Start();
return;
}
private void CrossThreadFlush()
{
while (true)
{
Thread.Sleep(2000);
FlushText();
}
return;
}
private delegate void FlushText_Delegate();
private void FlushText()
{
if (this.textBox1.InvokeRequired)
{
this.Invoke(new FlushText_Delegate(FlushText));
}
else
{
this.textBox1.Text = DateTime.Now.ToString();
}
return;
}InvokeRequired为true，表明当前调用Control的成员方法/成员变量的线程，与创建Control的线程，不是同一个线程，不能跨线程访问Control；为false，表明是同一个线程。
【1.4的代码，有待测试。。。】
1.5、总结
Control.Invoke(Delegate)、Control.BeginBeginInvoke(Delegate)，都会将Delegate封装的操作交给主线程运行，而当Delegate封装的操作是刷新Control时，就不会抛出“跨线程访问控件”的运行时异常了。
五、参考
C# InvokeRequired和Invoke-优快云博客
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