Question

I want to know how to refresh a wpf element before Thread.sleep() is executed. In the scenario below the Thread.sleep() call is executed first, then update the wpf element.

I tried this:

In the button_click event handler:

EDIT: To understand what I want, I added some variable assignations and comments.

 private void button_click(object sender, RoutedEventArgs e){
     //fist of all, set the static variable to_change to true, then Update GUI label
     to_change = true;
     Thread thread = new Thread(UpdateGUI);
     thread.Start();
     //Then sleep 1 second and ( With label changed)
     Thread.Sleep(1000);// one second
     //and lately reset the value of to_change to false and update the GUI again
     to_change = false;
     //UpdateGUI.
 }

And in UpdateGUI I have:

 private void UpdateGUI()
    {
        this.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
            (ThreadStart)delegate()
            {
                this.label_success.Content = "Successful!"; 
            }
            );
    }

Also I’ve tried with DispatcherPriority.Send which is the highest priority

I guess i’m missing some important concept.

Thanks in advance !

Answer 1

You can force WPF to process all of the items in its queue by Invoking to the Dispatcher an item that is a lower or equal priority to the task you want to execute. Just pass an empty delegate as the action, like this.

Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Normal, new Action(delegate { }));

This will work; however doing this should not be “normal”, and I’m curious why you need to sleep your main UI thread… The code you show above is scary, but I don’t know the big picture, so maybe there is a reason for this?