显示鼠标在地图上的坐标

<esri:Map x:Name="MyMap" WrapAround="True" MouseMove="MyMap_MouseMove">
            <esri:ArcGISTiledMapServiceLayer ID="MyLayer" 
                Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"/>
        </esri:Map>

        <Grid Width="355" Height="65" HorizontalAlignment="Right" VerticalAlignment="Top" Margin="0,15,15,0" >
            <Rectangle Stroke="Gray"  RadiusX="10" RadiusY="10" Fill="#77919191" Margin="0,0,0,6" >
                <Rectangle.Effect>
                    <DropShadowEffect/>
                </Rectangle.Effect>
            </Rectangle>
            <Rectangle Fill="#FFFFFFFF" Stroke="DarkGray" RadiusX="5" RadiusY="5" Margin="10,10,10,15"  />
            <StackPanel Canvas.Left="20" Canvas.Top="14" Margin="20,14,10,0">
                <TextBlock x:Name="ScreenCoordsTextBlock" 
                    HorizontalAlignment="Left" VerticalAlignment="Center" Text="Screen Coords: " TextWrapping="Wrap" FontWeight="Bold" />
                <TextBlock x:Name="MapCoordsTextBlock" 
                    HorizontalAlignment="Left" VerticalAlignment="Center" Text="Map Coords: " TextWrapping="Wrap" FontWeight="Bold" />
            </StackPanel>
        </Grid>


  private void MyMap_MouseMove(object sender, System.Windows.Input.MouseEventArgs args)
        {
            if (MyMap.Extent != null)
            {
                System.Windows.Point screenPoint = args.GetPosition(MyMap);
                ScreenCoordsTextBlock.Text = string.Format("Screen Coords: X = {0}, Y = {1}", 
                    screenPoint.X, screenPoint.Y);

                ESRI.ArcGIS.Client.Geometry.MapPoint mapPoint = MyMap.ScreenToMap(screenPoint);
                if (MyMap.WrapAroundIsActive)
                    mapPoint = ESRI.ArcGIS.Client.Geometry.Geometry.NormalizeCentralMeridian(mapPoint) as ESRI.ArcGIS.Client.Geometry.MapPoint;
                MapCoordsTextBlock.Text = string.Format("Map Coords: X = {0}, Y = {1}",
                    Math.Round(mapPoint.X, 4), Math.Round(mapPoint.Y, 4));
            }
        }