Solved! Go to Solution.
<esri:FeatureLayer.MapTip> <ContentControl ContentTemplate="{StaticResource MyFeatureLayerInfoWindowTemplate}" Content="{Binding}"/> </esri:FeatureLayer.MapTip>
<esri:FeatureLayer.MapTip> <ContentControl ContentTemplate="{StaticResource MyFeatureLayerInfoWindowTemplate}" Content="{Binding}"/> </esri:FeatureLayer.MapTip>