Testing to see if our 3.5 WPF application can be upgraded to 4.0. We make use of the WPF Toolkit - in particular the visual state manager. We have some custom controls that extend existing controls and have styling for the Invalid state. We also have a control template that we use for Validation.ErrorTemplate. In 3.5 both the Invalid state as well as the ErrorTemplate would be applied. Now in 4.0 I notice that if my control template defines the Invalid state and the control becomes invalid it will apply the invalid state but not the ErrorTemplate. If I comment out the Invalid state in the Xaml the ErrorTemplate starts getting applied.
Is this a bug in WPF new native VisualStateManager? Is it expected behavior? Am I doing something wrong? I have made no code or Xaml changes. All I did was to upgrade the project to 4.0 and remove all references to WPF Toolkit.