Silverlight addin for map viewer

I am looking for a custom add-in for the ArcGIS silverlight viewer. I need the ability to query a map layer by either a tabular pick list or a spatial entry. So for example, the user can select the plant layer and select to only see features that have knapweed for it's species. I want the ability to let them pick from a drop down list. Secondly they could draw a polygon on the screen and query the results of the plant layer that way too. We need it to be easily configurable and to be able to be added into the viewer for several maps.