How to deal with OSM from arcgis silverlight API

Communities Россия (Russia)
1

Dear Gurus!
I use arcgisonline.com services as follows:

        <esri:Map x:Name="Map" Background="White" WrapAround="true" Extent="6095000,6810000,6900000,7258000">

            <esri:ArcGISTiledMapServiceLayer ID="BaseLayer" 
                                            
                  Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"/> 

        </esri:Map>

Can anybody say how I can address to OSM services?