Thanks for your reply, Morten and Dominique. However, after I installed the new ArcGIS Silverlight API 2.0, and manually replaced my old referenced 1.2 dlls with the new 2.0 version dlls (ESRI.ArcGIS.Client ; ESRI.ArcGIS.Client.Behaviors and ESRI.ArcGIS.Client.Toolkit). Yet the whole program kind of messed up (I can't use the Intellisense in xaml any more and some error about no overload delegate for some event-handler). I have VS 2008 ( with Microsoft Silverlight 3 SDK; Microsoft Silverlight 3 Tools for Visual Studio 2008 SP1 -ENU; Microsoft Silverlight 4 Toolkit April 2010) intalled. Do I need to get the VS 2010 to make use of this new ESRI silverlight 2.0 API?
Many thanks,
Wei