Public Sub UnSelect() 

public void UnSelect()

<Grid x:Name="LayoutRoot">
  
  <!--
  Define a two SimpleFillSymbol objects in the Resources section of the XAML file. Also define a 
  SpatialReference for using best practices when adding Graphics to the GraphicsLayer.
  -->
  <Grid.Resources>
     
    <!--
    RedFillSymbol is the default for the polygon Graphic symbolization. CyanFillSimbol will be used to 
    denote a selected polygon Graphic.
    -->
    <esri:SimpleFillSymbol x:Key="RedFillSymbol" Fill="#66FF0000" BorderBrush="Red" BorderThickness="2" />
    <esri:SimpleFillSymbol x:Key="CyanFillSymbol" Fill="Cyan" BorderBrush="Cyan" BorderThickness="2" />
    
    <!-- 
    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 a few Graphics based upon polygon geometries and using the RedFillSymbol 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. Set the Map.Extent to that
  of an area where the sample Graphics are located.
  -->
  <esri:Map Background="White" HorizontalAlignment="Left" Margin="12,150,0,0" Name="Map1" 
            VerticalAlignment="Top" Height="318" Width="483" Extent="8.96,-63.28,178.76,48.51">
    <esri:ArcGISTiledMapServiceLayer ID="PhysicalTiledLayer" 
               Url="http://services.arcgisonline.com/ArcGIS/rest/services/ESRI_StreetMap_World_2D/MapServer"/>
    
    <esri:GraphicsLayer ID="MyGraphicsLayer" MouseLeftButtonDown="GraphicsLayer_MouseLeftButtonDown">
    
      <esri:GraphicsLayer.Graphics>
      
        <!-- 
        Define a few polygon Graphics using the StaticResources for the Symbol and SpatialReference.
        -->
        <esri:Graphic Symbol="{StaticResource RedFillSymbol}">
          <esri:Polygon SpatialReference="{StaticResource theSpatialReference}">
            <esri:Polygon.Rings>
              <esri:PointCollection>
                <esri:MapPoint X="110.039" Y="-20.303" />
                <esri:MapPoint X="132.539" Y="-7.0137" />
                <esri:MapPoint X="153.281" Y="-13.923" />
                <esri:MapPoint X="162.773" Y="-35.174" />
                <esri:MapPoint X="133.594" Y="-43.180" />
                <esri:MapPoint X="111.797" Y="-36.032" />
                <esri:MapPoint X="110.039" Y="-20.303" />
              </esri:PointCollection>
            </esri:Polygon.Rings>
          </esri:Polygon>
        </esri:Graphic>
        
        <esri:Graphic Symbol="{StaticResource RedFillSymbol}">
          <esri:Polygon SpatialReference="{StaticResource theSpatialReference}">
            <esri:Polygon.Rings>
              <esri:PointCollection>
                <esri:MapPoint X="110.039" Y="20.303" />
                <esri:MapPoint X="132.539" Y="7.0137" />
                <esri:MapPoint X="162.773" Y="35.174" />
                <esri:MapPoint X="111.797" Y="36.032" />
                <esri:MapPoint X="110.039" Y="20.303" />
              </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="87" HorizontalAlignment="Left" Name="TextBlock1" VerticalAlignment="Top" 
           Width="483" 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 using the Select and UnSelect Methods. When a 
           Graphic has been selected, a function will iterate over all the Graphics in the
           GraphicsLayer and render the symbology according to the selected value." />
           
</Grid>

private void GraphicsLayer_MouseLeftButtonDown(object sender, ESRI.ArcGIS.Client.GraphicMouseButtonEventArgs e)
{
  // This function selects/unselects a Graphic and then renders all the Graphics in the GraphicsLayer
  // based upon their selection value.
  
  // Alternate the selected state of the Graphic using the UnSelect and Select Methods.
  if (e.Graphic.Selected == true)
  {
    e.Graphic.UnSelect();
  }
  else if (e.Graphic.Selected == false)
  {
    e.Graphic.Select();
  }
  
  // Obtain the GraphicsLayer that was defined in XAML.
  ESRI.ArcGIS.Client.GraphicsLayer theGraphicsLayer = null;
  theGraphicsLayer = (ESRI.ArcGIS.Client.GraphicsLayer)(Map1.Layers["MyGraphicsLayer"]);
  
  // Get the GraphicsCollection from the GraphicsLayer.
  ESRI.ArcGIS.Client.GraphicCollection theGraphicsCollection = theGraphicsLayer.Graphics;
  
  // Render each Graphic in the GraphicsCollection with the appropriate symbology based upon
  // its selected state.
  RenderSelectedGraphicsDifferently(theGraphicsCollection);
}
            
public void RenderSelectedGraphicsDifferently(ESRI.ArcGIS.Client.GraphicCollection theGraphicsCollection)
{
  // This function obtains the polygon fill symbology that was defined in XAML and then renders
  // the correct SimpleFillSymbol depending on each Graphics selection state.
  
  // Get the SimpleFillSymbols for XAML
  ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol theSelectedSimpleFillSymbol = null;
  theSelectedSimpleFillSymbol = (ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol)(LayoutRoot.Resources["CyanFillSymbol"]);
  ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol theUnSelectedSimpleFillSymbol = null;
  theUnSelectedSimpleFillSymbol = (ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol)(LayoutRoot.Resources["RedFillSymbol"]);
  
  // Loop through all the Graphics in the GraphicCollection and render the correct symbology.
  // Note: If there a numerous Graphics this approach may not be efficient. Consider using a
  // VisualStateManager as a more efficient mechanism (see the Graphic.Selected Property code
  // example) to switching symbolgy based upon a selection state.
  foreach (ESRI.ArcGIS.Client.Graphic aGraphic in theGraphicsCollection)
  {
    if (aGraphic.Selected == true)
    {
      aGraphic.Symbol = (ESRI.ArcGIS.Client.Symbols.Symbol)theSelectedSimpleFillSymbol;
    }
    else
    {
    aGraphic.Symbol = (ESRI.ArcGIS.Client.Symbols.Symbol)theUnSelectedSimpleFillSymbol;
    }
  }
}

Private Sub GraphicsLayer_MouseLeftButtonDown(ByVal sender As System.Object, ByVal e As ESRI.ArcGIS.Client.GraphicMouseButtonEventArgs)
  
  ' This function selects/unselects a Graphic and then renders all the Graphics in the GraphicsLayer
  ' based upon their selection value.
  
  ' Alternate the selected state of the Graphic using the UnSelect and Select Methods.
  If e.Graphic.Selected = True Then
    e.Graphic.UnSelect()
  ElseIf e.Graphic.Selected = False Then
    e.Graphic.Select()
  End If
  
  ' Obtain the GraphicsLayer that was defined in XAML.
  Dim theGraphicsLayer As ESRI.ArcGIS.Client.GraphicsLayer
  theGraphicsLayer = CType(Map1.Layers("MyGraphicsLayer"), ESRI.ArcGIS.Client.GraphicsLayer)
  
  ' Get the GraphicsCollection from the GraphicsLayer.
  Dim theGraphicsCollection As ESRI.ArcGIS.Client.GraphicCollection = theGraphicsLayer.Graphics
  
  ' Render each Graphic in the GraphicsCollection with the appropriate symbology based upon
  ' its selected state.
  RenderSelectedGraphicsDifferently(theGraphicsCollection)
  
End Sub
            
Public Sub RenderSelectedGraphicsDifferently(ByVal theGraphicsCollection As ESRI.ArcGIS.Client.GraphicCollection)
  
  ' This function obtains the polygon fill symbology that was defined in XAML and then renders
  ' the correct SimpleFillSymbol depending on each Graphics selection state.
  
  ' Get the SimpleFillSymbols for XAML
  Dim theSelectedSimpleFillSymbol As ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol
  theSelectedSimpleFillSymbol = CType(LayoutRoot.Resources("CyanFillSymbol"), ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol)
  Dim theUnSelectedSimpleFillSymbol As ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol
  theUnSelectedSimpleFillSymbol = CType(LayoutRoot.Resources("RedFillSymbol"), ESRI.ArcGIS.Client.Symbols.SimpleFillSymbol)
  
  ' Loop through all the Graphics in the GraphicCollection and render the correct symbology.
  ' Note: If there a numerous Graphics this approach may not be efficient. Consider using a
  ' VisualStateManager as a more efficient mechanism (see the Graphic.Selected Property code
  ' example) to switching symbolgy based upon a selection state.
  For Each aGraphic As ESRI.ArcGIS.Client.Graphic In theGraphicsCollection
    If aGraphic.Selected = True Then
      aGraphic.Symbol = CType(theSelectedSimpleFillSymbol, ESRI.ArcGIS.Client.Symbols.Symbol)
    Else
      aGraphic.Symbol = CType(theUnSelectedSimpleFillSymbol, ESRI.ArcGIS.Client.Symbols.Symbol)
    End If
  Next
  
End Sub