Hi Tanya,In the ArcGIS Viewer for Silverlight you'll want to use MapApplication.Current.Map (from the Esri.ArcGIS.Client.Extensibility assembly) instead of a MapControl. Depending on how you are implementing your tool, you may wish to take a look at the Go To Coordinates sample we just released.Hope that helps,Katy
Katy Dalton | Technical Consultant
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