Whenever I try to use and EventSetter in my style, I get the following error :

Error 1 Value 'Expanded' cannot be assigned to property 'Event'. 'RoutedEventValueSerializer' ValueSerializer cannot convert from 'System.String'.

However, if I run the application everything works fine. This ends up being an rather annoying inconvenience as the visual editor for the window does not work when this error is being reported. Is this a known bug