Thanks for checking,Can you verify with a FeatrureLayer using OnDemand and a MaxResolution set (yes I was below this resolution when I first tryed to turn it on).<esri:FeatureLayer ID="FLWaterLines" Url="http://***/rest/services/GIS_App_ENG/MapServer/2"
FeatureSymbol="{StaticResource LineWaterBlue}" Mode="OnDemand" OutFields="*" MaximumResolution="3"
Visible="False" x:Name="FLWL" Where="WATERLINETYPE='WATERMAIN'">
<Button x:Name="MTWater"
Style="{StaticResource MenuItem}"
Content="Map Tip Water">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<esriBehaviors:ToggleLayerAction LayerID="FLWaterLines" TargetName="MyMap"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>
Thanks again