While looking at the ESRI samples for the 2.0 API I notice the reference to the System.Windows.Interactivity namespace in the XAML. When I tried to add this reference using VS2010 I am unable to locate this. Going back to VS2008(on another machine) I notice the reference to System.Windows.Interactivity is located within the Expression 3 SDK. ( I do not have the Expression 4 yet). Is Expression required when referencing System.Windows.Interactivity?
