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I have a ContentPresenter that switches between 2 states ("editor" and "viewer"). The states have different heights and different values of Content and ContentTemplate properties.

In one state change I resize the control by playing a Storyboard and in reaction to Storyboard.Completed event I change Content/Template properties.

It works basically ok, except I observed occasional flickering. When playing in debugger I observed that modifying above properties in Completed handler may cause strange screen effects (portions of the screen empty, extra shading, lines etc.) that the user observes as flickering.

However, whenever I postponed the ContentPresenter changes by using Dispatcher.BeginInvoke(), the problems seem to disappear. (More testing needed.)

Anyone has an explanation? On the web you'll find numerous code examples that perform UI changes in Storyboard.Completed handler, hence I find it a bit strange.

Jan Slodicka
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  • I recognized when working with more than one storyboard and somewhere in the app is threading used, the second storyboard does not raise his event. I am working with the backgroundworker now but this is not a solution. But I can debug it. A WPF example is found here which I think is good: http://stackoverflow.com/questions/80388/wpf-data-triggers-and-story-boards – goldengel Aug 23 '11 at 13:28

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I suspect it may be more due to timing than needing to be on the UI thread. Try doing a Sleep for a second or so before changing the Content/Template properties instead of using Dispatcher.BeginInvoke(). If the flicker is gone then perhaps trying to change those properties while the Content was busy resizing itself during the storyboard was the culprit - perhaps assigning a fixed size or otherwise disabling the constant resizing during the storyboard would help. That's just a guess though, I'd have to see a sample to really figure it out. If you can make a small sample to reproduce it I'd gladly look at it.

Austin Thompson
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  • Thanks for suggestion. I worked on the problem for 2 days and managed to reduce it, but not remove it. Please look at http://stackoverflow.com/questions/6945235/bug-in-storyboard-animation where I posted more details. – Jan Slodicka Aug 29 '11 at 09:10