Dispatcher causes NullReferenceException

Question

This line of code, which is run every 10 secs, normally updates my UI, and works perfectly.

Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new UIUpdateDelegate(this.UIUpdate));

I have a regular file-menu with an exit option which runs Application.Current.Shutdown();
If I use the file => exit approach it works fine. However, if I close the application with the X button in the upper right corner,
the Dispatcher causes an unhandled nullreferenceexception, but not always.

Any ideas on what is happening?

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http://www.catb.org/~esr/faqs/smart-questions.html#intro

Answer 1

You'll need to post to the Windows Presentation Foundation forum.

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Hans Passant.

Answer 2

My bad.

I'm giving this one a bump since I obviously posted in the wrong forum, and now it's far down the list :)

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http://www.catb.org/~esr/faqs/smart-questions.html#intro

Answer 3

Put a Null check:

if(this !=null)
    Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new UIUpdateDelegate(this.UIUpdate));

Answer 4

Ok, I'm trying that, thanks.
Why is that? The timer elapses during object disposal and the method is no longer available to run?

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http://www.catb.org/~esr/faqs/smart-questions.html#intro

Answer 5

Event handling and dispose of objects are working in different threads, this is the only possibility.