NO! Don't crash!

Question

Is there any reason why the following code should crash the current windows form it's operating in? It works if I take the screenshot quickly, but if I leave the windows up for a few seconds my windows form gets a little hour glass in front of it and wont respond to anything, then I ussually have to kill it the program the hard way.

private void ActiveWindowCaptureAlert()

{

MessageBox.Show("Select the window you want a screenshot of, then press capture!");

while (this.Handle == GetForegroundWindow())

{

Thread.Sleep(10); //sleeping for even 100 seems to make the loop crash

}

while (this.Handle != GetForegroundWindow())

{

hOld = GetForegroundWindow();

Thread.Sleep(10);

}

// ActiveWindowCapture();

}

hOld is a windows handle, as you may have guessed...

Alan · Answer

It sounds to me as though the combination of Thread.Sleep and GetForegroundWindow may be producing a deadlock. Rather than using Thread.Sleep I'd try an old fashioned way of producing a delay a 'do nothing' for loop. On my (slow) home machine the following line produces a delay of around 100 milliseconds: for(int i = 0; i Another possibility would be to use an event - Deactivate or LostFocus - to tell you when the current form has lost the focus.

Adam Turner · Answer

Actually it progresses through the loops. Otherwise it would never call the function to create the screenshot. But the thing is it only seems to work if it's done under a few seconds otherwise it crashes. But if what you're saying is true why is it true and why does it appear to go through the loop to the intended function? I guess I'm just daft (and new to C#/windows programming) but I'm not seeing it.

Alan C Balkany · Answer

If either loop loops once it will loop forever. I don't think that's what you intended.