Public Property Selected As Boolean

public bool Selected {get; set;}

<Grid x:Name="LayoutRoot">
  
  <!-- 
  Define a FillSymbol in the Resources section of the XAML file. The FillSymbol uses a ControlTemplate
  to define two VisualStateGroups which automatically switch symbology on the GraphicsLayer depending 
  on whether individual Graphic objects are selected or not. Also define a SpatialReference for using
  best practices when adding Graphics to the GraphicsLayer.
  -->
  <Grid.Resources>
    <esriSymbols:FillSymbol x:Key="SelectFillSymbol">
      <esriSymbols:FillSymbol.ControlTemplate>
        <ControlTemplate>
          
          <!-- 
          Provide the default look of the FillSymbol for the polygon Graphic (a solid blue fill with 
          black edges). 
          -->
          <Path x:Name="Element" Stroke="Black" StrokeStartLineCap="Round" StrokeThickness="2"
				StrokeLineJoin="Round" StrokeEndLineCap="Round" Fill="Blue">
          
            <!-- 
            Learn more about the VisualStateManager in the MSDN document:
            http://msdn.microsoft.com/en-us/library/system.windows.controls.controltemplate(v=VS.95).aspx 
            Note: The VisualStateManager Class was newly added in the .NET Framework v4.0. If you are 
            running the .NET Framework v3.5 then you can download and Reference the WPFToolkit on 
            Codeplex (http://wpf.codeplex.com) to take advantage of the VisualStateManager Class.
            -->
            <VisualStateManager.VisualStateGroups>
              
              <VisualStateGroup x:Name="SelectionStates">
                
                <!--
                By specifying an empty Unselected state, unselecting the graphic will set the
                values back to their original value. The use of a Duration and Storyboard provides  
                a smooth transition back. Note that it take .75 seconds for the Graphic to be
                selected and .25 seconds to go back to the original state.
                -->
                <VisualState x:Name="Unselected" >
                  <Storyboard>
                    
                    <!-- 
                    Note how the To="Blue" Attribute matches the default Fill Attribute value of
                    the Path x:Name="Element" for defining the Polygon's Symbology.
                    -->
                    <ColorAnimation Storyboard.TargetName="Element" To="Blue"  Duration="00:00:00.25"
									Storyboard.TargetProperty="(Path.Fill).(SolidColorBrush.Color)"/>
                  </Storyboard>
                </VisualState>
                                
                <VisualState x:Name="Selected">
                  <Storyboard>
                    
                    <!-- 
                    The To="Cyan" Attribute will become the Fill Atrribute value for the Selected state
                    of the Path x:Name="Element" for defining the Polygon's Symbology.
                    -->
                    <ColorAnimation Storyboard.TargetName="Element" To="Cyan" Duration="00:00:00.75"
 									Storyboard.TargetProperty="(Path.Fill).(SolidColorBrush.Color)"/>
                  </Storyboard>
                </VisualState>
                
              </VisualStateGroup>
                            
            </VisualStateManager.VisualStateGroups>
                      
          </Path>
          
        </ControlTemplate>
      </esriSymbols:FillSymbol.ControlTemplate>
    </esriSymbols:FillSymbol>
    
    <!-- Define a SpatialReference object that has the same WKID as the ArcGISTiledMapServiceLayer in
         the Map. This will allow for the Graphics in the GraphicsLayer to line up properly. -->
    <esri:SpatialReference x:Key="theSpatialReference" WKID="4326"/>
    
  </Grid.Resources>
  
  <!-- 
  Add a Map control with an ArcGISTiledMapServiceLayer and a GraphicsLayer. The GraphicsLayer will
  contain several Graphics based upon Polygon geometries and using the SelectFillSymbol for the 
  symbolization. By default the Graphics are not selected. The MouseLeftButtonDown Event on the 
  GraphicsLayer has been specified to wire-up code-behind functionality.
  -->
  <esri:Map Background="White" HorizontalAlignment="Left" Margin="36,51,0,0" Name="Map1" 
            VerticalAlignment="Top" Height="318" Width="483">
      
    <esri:ArcGISTiledMapServiceLayer ID="PhysicalTiledLayer" 
               Url="http://services.arcgisonline.com/ArcGIS/rest/services/ESRI_StreetMap_World_2D/MapServer"/>
    
    <!-- 
    The MouseLeftButtonDown Event only fires when clicking with the left mouse button over a Graphic.
    It will not fire if clicked over areas of the Map Control where there are no Graphics. 
    -->
    <esri:GraphicsLayer ID="MyGraphicsLayer" MouseLeftButtonDown="GraphicsLayer_MouseLeftButtonDown">
      
      <esri:GraphicsLayer.Graphics>
        
        <!-- 
        Define several Polygon based Graphics using the StaticResources for the Symbol and SpatialReference.
        -->
            
        <esri:Graphic Symbol="{StaticResource SelectFillSymbol}">
          <esri:Polygon SpatialReference="{StaticResource theSpatialReference}">
            <esri:Polygon.Rings>
              <esri:PointCollection>
                <esri:MapPoint X="10" Y="-20" />
                <esri:MapPoint X="32" Y="-7" />
                <esri:MapPoint X="53" Y="-13" />
                <esri:MapPoint X="62" Y="-35" />
                <esri:MapPoint X="33" Y="-43" />
                <esri:MapPoint X="11" Y="-36" />
                <esri:MapPoint X="10" Y="-20" />
              </esri:PointCollection>
            </esri:Polygon.Rings>
          </esri:Polygon>
        </esri:Graphic>
        
        <esri:Graphic Symbol="{StaticResource SelectFillSymbol}">
          <esri:Polygon SpatialReference="{StaticResource theSpatialReference}">
            <esri:Polygon.Rings>
              <esri:PointCollection>
                <esri:MapPoint X="10" Y="20" />
                <esri:MapPoint X="32" Y="7" />
                <esri:MapPoint X="62" Y="35" />
                <esri:MapPoint X="11" Y="36" />
                <esri:MapPoint X="10" Y="20" />
              </esri:PointCollection>
            </esri:Polygon.Rings>
          </esri:Polygon>
        </esri:Graphic>
        
        <esri:Graphic Symbol="{StaticResource SelectFillSymbol}">
          <esri:Polygon SpatialReference="{StaticResource theSpatialReference}">
            <esri:Polygon.Rings>
              <esri:PointCollection>
                <esri:MapPoint X="5" Y="17" />
                <esri:MapPoint X="5" Y="5" />
                <esri:MapPoint X="-10" Y="8" />
                <esri:MapPoint X="-12" Y="18" />
                <esri:MapPoint X="5" Y="17" />
              </esri:PointCollection>
            </esri:Polygon.Rings>
          </esri:Polygon>
        </esri:Graphic>
        
      </esri:GraphicsLayer.Graphics>
    </esri:GraphicsLayer>
  </esri:Map>
  
  <!-- Provide the instructions on how to use the sample code. -->
  <TextBlock Height="40" HorizontalAlignment="Left" Name="TextBlock1" VerticalAlignment="Top" 
             Width="616" TextWrapping="Wrap" Margin="12,12,0,0" 
             Text="Click on the Polygon Graphics with the left mouse button in the Map Control to 
             change their Selection value and Symbology. The XAML VisualStateManager in the 
             FillSymbol's ControlTemplate performs the work for swapping the symbology." />
    
  
</Grid>

private void GraphicsLayer_MouseLeftButtonDown(object sender, ESRI.ArcGIS.Client.GraphicMouseButtonEventArgs e)
{
  
  // Alternate between setting the Graphic's Selected property to true and false depending on where the
  // user clicks it with the left mouse button. The transitioning from one Symbol to another on the Graphic
  //based upon its Selected state is exclusively handled in XAML using the VisualStateManager Class.
  e.Graphic.Selected = ! (e.Graphic.Selected);
  
  // Helper notes:
  // -------------
  // sender is the ESRI.ArcGIS.Client.Graphic.GraphicsLayer object
  // e.StylusDevice is the System.Windows.Input.MouseEventArgs.StylusDevice Property
  // e.StylusDevice.DeviceType is a TabletDeviceType Enumeration value of (Mouse, Stylus, Touch)
  // e.OriginalSource is a System.Windows.Shapes.Path
  // e.Graphic is the Graphic for which the MouseLeftButtonDown occured over 
  
}

Private Sub GraphicsLayer_MouseLeftButtonDown(ByVal sender As System.Object, ByVal e As ESRI.ArcGIS.Client.GraphicMouseButtonEventArgs)
  
  ' Alternate between setting the Graphic's Selected property to true and false depending on where the
  ' user clicks it with the left mouse button. The transitioning from one Symbol to another on the Graphic
  'based upon its Selected state is exclusively handled in XAML using the VisualStateManager Class.
  e.Graphic.Selected = Not (e.Graphic.Selected)
  
  ' Helper notes:
  ' -------------
  ' sender is the ESRI.ArcGIS.Client.Graphic.GraphicsLayer object
  ' e.StylusDevice is the System.Windows.Input.MouseEventArgs.StylusDevice Property
  ' e.StylusDevice.DeviceType is a TabletDeviceType Enumeration value of (Mouse, Stylus, Touch)
  ' e.OriginalSource is a System.Windows.Shapes.Path
  ' e.Graphic is the Graphic for which the MouseLeftButtonDown occured over 
  
End Sub