How do I wait to Timer finish and then return from function?

Question

I want to wait to a timer finish and then return from a function. I tried this:

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

But it didn't work and the function returned before the timer really finished. Here's the full function:

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;
}

score 5 · Answer 1 · answered Nov 11 '14 at 21:44

5

I think what you actually want is to wait until the browser is ready. If so you can use a loop like this, and instead of Application.DoEvents() I recommend using async/await feature:

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

Or better you can handle DocumentCompleted event of WebBrowser.

answered Nov 11 '14 at 21:44

Selman Genç

100,147
13
119
184

I did it work, thanks! but if I call my function after that loop, the contentes loaded by ajax isn't available :( – Jack Nov 15 '14 at 01:51

Ludovic Feltz · Answer 2 · 2014-11-14T14:35:38.477

1

You can use a Thread instead of a Timer. Launch your waiting method in a Thread and simply wait it to finish with thread.IsAlive.

Your code must look like this:

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;

edited Nov 14 '14 at 14:35

answered Nov 14 '14 at 13:51

Ludovic Feltz

11,416
4
47
63

Have you tested it in a page with some contentes loaded by ajax? the function return before that ajax stuff is loaded – Jack Nov 14 '14 at 18:26

score 1 · Answer 3 · answered Nov 20 '14 at 06:51

Instead of using Await/Async and change the method signature you could use CountdownEvent and threading.

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;

}

The CountdownEvent will block the current thread until the counter reaches 0. Since the Timer class uses a ThreadPool for its callback, that event will still fire and work as normal.

score 1 · Answer 4 · answered Nov 20 '14 at 11:57

I will not go into how good or bad this approach is. But you can simply do this with a flag.

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;
}

And you should probably put a Thread.Sleep in the while loop also.

score 1 · Answer 5 · answered Nov 20 '14 at 19:49

1

Simply put some_value into a class-level variable, then have the timer raise an event. Any function calling your function can (before the call) subscribe to the event and then handle it.

answered Nov 20 '14 at 19:49

How do I wait to Timer finish and then return from function?

5 Answers5