Hello Yossi Naar,
The reason for this warning is that before we start an animation we stop the "opposite" animation (i.e. before collapsing we stop the expand animation). The two animations are created in Xaml and run by code in the controls.
Unfortunately in WPF we cannot really check if an animation is running or not. For example if you have this code:
var board =
you will see the same exception. If you try calling board.GetCurrentState()
an InvalidOperationException is thrown because this animation has not started before. Ironically we need the current state to check if the animation is running or not. We could possibly track and transfer the current state of the animation to avoid stopping it before it starts for the first time but this will add more overhead in the animations.
Unless we find an acceptable workaround we will prefer to have the warning but not try-catch any exceptions.
We are aware of this issue and you can track and vote for it here:
the Telerik team
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