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Solved

Wake me up in 500ms

Posted on 2006-07-09
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Last Modified: 2010-04-16
Hi,
I have a requirement that when a button is clicked, I should wait 500ms and than open a message box.
However, when i use the Thread.Sleep(500) method, the GUI get freezed.

So what I need is some sort of mechanism that I supply a callback function to be called after a certain amount of milliseconds.

I know I can use timers, but I don't want to add a timer to my class and activate it, just for that delay.

So is there a function like this: InvokeAfterDelay(Delegate callback, int milliseconds) ?
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Question by:PHILIPS_MED
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vo1d earned 300 total points
ID: 17067980
if you use the sleep method, the app running thread is paused.

if you dont want the control timer object, use the Thread.Timer object.
it is a timer object, which comes from the threadpool.
implement that timer object in your app, which interval is set to 500.
in the click eventhandler of your button, start the timer.
in the delegate of your timer, stop the timer first and show the messagebox.
this timer is a lightweight timer and needs nearly no resources.

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Expert Comment

by:vo1d
ID: 17067994
sorry, the namespace for that timer object is:
System.Threading.Timer .
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Author Comment

by:PHILIPS_MED
ID: 17068323
Hi vo1d,
If I understood you correctly, this is what I should put on the button.Click event handler:

new System.Threading.Timer(new TimerCallback(ShowMessageBox), null, 500, Timeout.Infinite);

And the timer will automatically stop and dispose itself?
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Expert Comment

by:Mike Tomlinson
ID: 17068552
For longer delays, you can use code like below (VB.Net example):

    Private Sub Delay(ByVal DelayInSeconds As Integer)
        Dim ts As TimeSpan
        Dim targetTime As DateTime = DateTime.Now.AddSeconds(DelayInSeconds)
        Do
            ts = targetTime.Subtract(DateTime.Now)
            Application.DoEvents() ' keep app responsive
            System.Threading.Thread.Sleep(50) ' reduce CPU usage (keep value small to avoid lockups)
        Loop While ts.TotalSeconds > 0
    End Sub
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Expert Comment

by:vo1d
ID: 17068578
correct.
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Expert Comment

by:vo1d
ID: 17068583
your ShowMessageBox should look like this:
public void ShowMessageBox(Object stateInfo)
        {            
            MessageBox.Show("whatever");
        }
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