Hi,
Typically these issues are caused by an old version of the System.Windows.Interactivity.dll. Unfortunately, because this DLL gets installed by the Blend SDK, it is possible that Visual Studio replaces the reference to this DLL in your application with the one that was installed with Blend. It is very important to make sure that you always use the latest version of this DLL otherwise the application will work but the design time experience will get impacted negatively.
Thanks
Laurent
Typically these issues are caused by an old version of the System.Windows.Interactivity.dll. Unfortunately, because this DLL gets installed by the Blend SDK, it is possible that Visual Studio replaces the reference to this DLL in your application with the one that was installed with Blend. It is very important to make sure that you always use the latest version of this DLL otherwise the application will work but the design time experience will get impacted negatively.
Thanks
Laurent