如何等待Timer完成然后从函数返回？

Question

我想等到计时器完成然后从函数返回。 我试过这个：

while(timer1.Enabled)
{
    Application.DoEvents();
}
return value;

但它没有工作，函数在计时器真正完成之前返回。 这是完整的功能：

System.Windows.Forms.Timer timer1 = new System.Windows.Forms.Timer();
int[] foo()
{

    do_something1();

    int[] some_value;

    timer1.Interval = 1000;
    timer1.Tick += new EventHandler(delegate(object o, EventArgs ea)
    {
        if (browser.ReadyState == WebBrowserReadyState.Complete)
        {
            timer1.Stop();
            baa(some_value);
        }
    });
    timer1.Start();

    while (timer1.Enabled)
    {
        Application.DoEvents();
    }

    return some_value;
}

Answer 1

我认为你真正想要的是等到浏览器准备好了。 如果是这样，你可以使用这样的循环，而不是Application.DoEvents()我建议使用async/await功能：

while(browser.ReadyState != WebBrowserReadyState.Complete)
{ 
   // you need to make your method async in order to use await
   await Task.Delay(1000);
}
// do your job

或者你可以更好地处理WebBrowser的DocumentCompleted事件。

Answer 2

我不会讨论这种方法有多好或多坏。 但你可以用旗帜做到这一点。

System.Windows.Forms.Timer timer1 = new System.Windows.Forms.Timer();
int[] foo()
{

    do_something1();

    int[] some_value;

    bool doneWaiting = false;

    timer1.Interval = 1000;
    timer1.Tick += new EventHandler(delegate(object o, EventArgs ea)
    {
        if (browser.ReadyState == WebBrowserReadyState.Complete)
        {
            timer1.Stop();
            baa(some_value);
            doneWaiting = true;
        }
    });
    timer1.Start();

    while (!doneWaiting)
    {
        Application.DoEvents();
    }

    return some_value;
}

你应该在while循环中放一个Thread.Sleep。

Answer 3

您可以使用Thread而不是Timer 。 在Thread中启动等待方法，然后等待它完成thread.IsAlive 。

您的代码必须如下所示：

int[] some_value;

int intervalle = 1000;
Thread thread = new Thread(new ThreadStart(delegate()
{
    while (true)
    {
        Thread.Sleep(intervalle);
        if (browser.ReadyState == WebBrowserReadyState.Complete)
        {
            baa(some_value);
            return;
        }
    }                
}));
thread.Start();

while (thread.IsAlive)
{
    Application.DoEvents();
}

return some_value;

Answer 4

而不是使用Await / Async并更改方法签名，您可以使用CountdownEvent和线程。

using System.Theading;
System.Windows.Forms.Timer timer1 = new System.Windows.Forms.Timer();

int[] foo()
{
  int numberOfIterations = interval time * number of intervals; // initialize this to the proper number of times to decrement the counter. If we are decrementing every 1000 ms
  CountdownEvent countDown = new CountdownEvemt(numberOfIterations);
  do_something1();

  int[] some_value;

  timer1.Interval = 1000;
  timer1.Tick += new EventHandler(delegate(object o, EventArgs ea)
  {
      if (browser.ReadyState == WebBrowserReadyState.Complete)
      {
          timer1.Stop();
          baa(some_value);
          // since this seems where you want to shut down the method we need to trigger the countdown
          int countLeft = countDown.CurrentCount;
          countDown.Signal(countLeft); 
      } else {
          if(countDown.CurrentCount - 1 == 0) {
              countDown.Reset(); // we don't want to finish yet since we haven't reached the proper end condition so reset the counter
          }
          countDown.Signal(); // will decrement the counter
      }
  });
  timer1.Start();

  countDown.Wait(); // will wait 'til the counter is at 0 before continuing
   return some_value;

}

CountdownEvent将阻塞当前线程，直到计数器达到0.由于Timer类使用ThreadPool进行回调，因此该事件仍将触发并正常工作。

Answer 5

只需将some_value放入类级变量，然后让计时器引发一个事件。 调用你的函数的任何函数都可以（在调用之前）订阅事件然后处理它。