Check out this sdk example:http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#FeatureLayerMapTipsIt uses featurelayers so if you are adding all your layers as a dynamic service and then do something like the example you might be adding the layers twice. Why not just use graphic layer maptips. http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#GraphicsMapTipAdd the graphics on Initial start up and if you have the layers already added by your dynamic map service set your graphic layer colors as fully transparent something like
<esri:SimpleMarkerSymbol x:Name="MapTipMarkerSymbol" Color="#00FFFFFF" Size="12" Style="Circle" />
Also when I have used this maptips for graphics layer in the past I always need to add this line in the code behind // Return geometry with result features query.ReturnGeometry = true;in the example here is where you would add it:
query.OutFields.Add("*");
query.Where = "POP1990 > 100000";
//ADD HERE
// Return geometry with result features
query.ReturnGeometry = true;
QueryTask queryTask = new QueryTask("http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Specialty/ESRI_StatesCitiesRivers_USA/MapServer/0");
Not sure why but when I'm using my own services I need this line, when I'm consuming ESRI services (for the graphic layer creatation) I don't need it...WIERD:pJ