Grrrr!!!  This was one of the most frustrating issues I've encountered in WPF.  Unlike Winforms where you can always call a .refresh or .invalidate method on a control, no similar functionality exists in WPF.  Here's the scenario that caused my problem.  I had a splash screen that sets up some things in my applicatoin.  The last thing it does is declare a new instance of my main form and then show it.  The "new" method of my form takes about 3 seconds to run.  Prior to the statement creating the new form we change a status textblock on our splash screen to say "Building User Interface..."  Unfortunately, no matter what I did, I could NOT get this visual representation of the text to actually display before the new instance of our main form (which locks the UI and takes 3 seconds) began.  I tried playing with the  InvalidateVisual, UpdateLayout, InvalidateProperty methods on the textblock, the splash form, etc. withno luck.  Basically what I needed was a "DoEvents" type of statement.  I ended up doing this withe following code:

Dim datNow As DateTime = Now
While Now.Subtract(datNow).TotalMilliseconds < 100
    Application.Current.Dispatcher.Invoke(DispatcherPriority.Background, New ThreadStart(AddressOf doNothing)) ' wait for 100 ms to update textbox...STUPID STUPID STUPID
End While

By allowing it to "chill" for 100 milliseconds it lets the UI render the new text on the textblock control.

I do not like this solution, it is a kludge and there HAS to be a better way to force the visual update of a control.  I can't spend any more time on such a menial task.  If anyone has any suggestions they'd be much appreciated!

Sean