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How to force a WPF Control to Refresh mid-processing

Posted on 2006-11-24
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5,933 Views
Last Modified: 2012-06-27
Peace be with you all,

In trying to adapt to the new WPF model, I have not figured out how to update a
control in the midst of processing.

--------------
//non-complete example:

Button buGo;
TextBlock tbOutput;

private void buGo_Click( object sender, RoutedEventArgs e ) {
  int i;
  for (i=0; i < 1000; ++i) {
    tbOutput.Text = i.ToString();
}
--------------

After clicking on buGo, the program runs and then tbOutput changes to '999'.
What I want is to see each individual number '0' ... '999' in tbOutput after
each modification, even if I have to make a fct call manually after setting
tbOutput.Text.

In System.Windows.Forms, I could call tbOutput.Refresh() which would
force the control to re-render itself immediately.

I am having no luck finding a corollary in the WPF and am guessing that
some sort of threading solution may be the only way to accomplish this,
meaning that I may have to split out my processing into a second thread,
which makes an 'Invoke'-ish type call back to the original thread that
created the controls.

Thanks in advance,
Robert McCall

PS: *MODERATORS* Might I suggest 3 new .NET sub-categories:  WPF, WCF and WF/WWF?
   Now that Microsoft has officially released .NET 3.0, these questions are gonna start flooding in, maybe.
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Question by:mihrlogic
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6 Comments
 
LVL 48

Expert Comment

by:AlexFM
ID: 18010526
Does Application.DoEvents help?
0
 

Author Comment

by:mihrlogic
ID: 18010622
AlexFM,

No, there is no such call in the WPF ~ Windows Presentation Foundation.  It's a completely
different model; and, FYI, Application.DoEvents() exposes your program to all kinds of problems
with re-entrancy, so it is better to use Obj.Refresh() instead.

Thanks anyway,
Robert
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LVL 48

Accepted Solution

by:
AlexFM earned 500 total points
ID: 18010691
Try Dispatcher.UpdateRender(). In any case, you need to add some kind of sleep to this code to see that something changes.
Of course, threading is better solution. WPF has some kind of Invoke methods which allow to talk with WPF controls from worker threads - exactly like in Windows Forms.

In cheap DoEvents solution, reentrance problems are solved by disabling some UI elements. This is some information about WPF DoEvents:
http://shevaspace.spaces.live.com/blog/cns!FD9A0F1F8DD06954!411.entry?_c11_blogpart_blogpart=blogview&_c=blogpart#postcns!FD9A0F1F8DD06954!411
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