To achieve your goal you have to keep in mind the following things:
1. The VisualStateManager has to be used in a ControlTemplate or a UserControl, cannot be set like this in to the control.
2. The easiest way to manipulate animation is using Expression Blend.
3. The ContextMenu already has an animation for the Opacity.
If you want to open the menu with VisualStateManager, the VisualStateManager has to be to the UserControl and animate the IsOpen property of the Menu, not the Opacity. Instead of DoubleAnimationUsingKeyFrames you can use the ObjectAnimationUsingFeyFrames. Then, change the TargetProperty to IsOpen. Change the
Hope this information helps. If you have further questions please let us know.
the Telerik team
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