Map not showing in Silverlight application is mostly common but always easy to resolved problem. Just follow these steps to check where the issue is:1. Ensure your map service is running by displaying it in Arcmap or Javascript API(from services directory);2. Ensure you have the cross domain file in your web server and in the right place;3. Ensure using the right class to add the map service. Note the difference between ArcGISDynamicMapServiceLayer and ArcGISTiledMapServiceLayer;4. If now the problem remains, just using Fiddler or Firebug tools to check what happened during the map image loading course.
