This method implementation is incorrect, it violates MVVM pattern in a way that your ViewModel access the "Dispatcher" object (which is specific to UI). I think this needs a little rewrite to follow the model of "OnRequestShowNodeHelp" in the same file. As a quick look through other parts of InfoBubbleViewModel, I noticed it has information about UI -- "FrameStrokeThickness" and "FrameStrokeColor", do we have a reason that these UI-specific information must be stored in ViewModel?