Public Property NoDataColor As Nullable(Of Color)

public Nullable<Color> NoDataColor {get; set;}

<Grid x:Name="LayoutRoot">
  
  <!-- Add a Map Control. -->
  <esri:Map Background="White" HorizontalAlignment="Left" Margin="12,113,0,0" Name="Map1" 
            VerticalAlignment="Top" Height="367" Width="616" 
            Extent="-14005525,5619647,-13180689,6111067">
  
    <!-- Add an ArcGISTiledMapServiceLayer. -->
    <esri:ArcGISTiledMapServiceLayer ID="Topo" 
            Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer"/>
    
    <!-- 
    There are several ways to specify a System.Windows.Media.Color Structure for the ArcGISImageServiceLayer.NoDataColor 
    Property in XAML. The following three examples of the NoDataColor Property all yield the same results for the color BLACK: 
    NoDataColor="#000000" <== using the #rrggbb methodology
    NoDataColor="#FF000000" <== using the #aarrggbb methodology
    NoDataColor="Black" <== using the predefinedColor methodology
          
    The following MSDN help documents provide more information on the System.Windows.Media.Color Structure:
    http://msdn.microsoft.com/en-us/library/system.windows.media.color(v=vs.95).aspx
    http://msdn.microsoft.com/en-us/library/system.windows.media.colors(v=vs.95).aspx
      
    In order to have the NoDataColor Property return an image where the NoDataColor pixels are transparent the 
    ArcGISImageServiceLayer.ImageFormat must use a lossless compression. Valid lossless compression types are:
    PNG24, PNG8, and JPGPNG.
    
    NOTES:
    If you get the NoDataColor value wrong the NoDataColor pixels still show but they will just not be transparent.
    
    Alpha values are not used by the ArcGIS Server REST service. Hence if you use the #aarrggbb methodology to specify 
    the NoDataColor, the aa part is essentially ignored.
          
    This does not work in Silverlight. It is WPF only!:
    <esri:ArcGISImageServiceLayer.NoDataColor>
        <Color A="255" R="0" G="0" B="0"/>
    </esri:ArcGISImageServiceLayer.NoDataColor> 
    -->
    <esri:ArcGISImageServiceLayer x:Name="MyArcGISImageServiceLayer"
              Url="http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Portland/CascadeLandsat/ImageServer" 
              ImageFormat="PNG8" NoDataColor="Black" >
    </esri:ArcGISImageServiceLayer>
    
  </esri:Map>
  
  <!-- Add controls to demonstrate the effect of changing the ArcGISImageServiceLayer.NoDataColor. -->
  <Button Content="Change NoDataColor" Height="23" HorizontalAlignment="Left" Margin="12,84,0,0" 
          Name="Button1" VerticalAlignment="Top" Width="151" Click="Button1_Click"/>
  <RadioButton Content="Black" Height="16" HorizontalAlignment="Left" Margin="169,87,0,0" 
               Name="rb_Black" VerticalAlignment="Top" IsChecked="True" />
  <RadioButton Content="Red" Height="16" HorizontalAlignment="Left" Margin="233,87,0,0" 
               Name="rb_Red" VerticalAlignment="Top" />
  
  <!-- Provide the instructions on how to use the sample code. -->
  <TextBlock Height="78" HorizontalAlignment="Left" Name="TextBlock1" VerticalAlignment="Top" Width="640" 
         TextWrapping="Wrap" Text="Click either the Black or Red radio button and then click the 'Change NoDataColor' 
             button to see the effect of modifying the ArcGISImageServiceLayer.NoDataColor Property. By choosing the 
             Black radio button the NoData pixels will be made transparent. Setting the NoDataColor to any other color 
             other than what is defined in the ArcGIS Server map service as the as the NoDataColor will result in the 
             NoData pixels being displayed." />
</Grid>

// The following MSDN help documents provide more information on the System.Windows.Media.Color Structure:
// http://msdn.microsoft.com/en-us/library/system.windows.media.color(v=vs.95).aspx
// http://msdn.microsoft.com/en-us/library/system.windows.media.colors(v=vs.95).aspx
// 
// TIP:
// Use the Microsoft Calculator in the 'Programmer' mode see what a Dec and Hex equivalents are.
  
private void Button1_Click(object sender, System.Windows.RoutedEventArgs e)
{
  // Get the ArcGISImageServiceLayer defined in XAML.
  ESRI.ArcGIS.Client.ArcGISImageServiceLayer myArcGISImageServiceLayer = (ESRI.ArcGIS.Client.ArcGISImageServiceLayer)Map1.Layers[1];
  
  if (rb_Black.IsChecked == true)
  {
    // The NoData values that were defined in the ArcGIS Server ArcGISImageServiceLayer are BLACK. Only when
    // the ArcGISImageServiceLayer.NoDataColor value exactly matches will the NoData pixels be displayed
    // as transparent.
    //
    // The following three code-behind Options all produce the same result:
    
    //Option #1
    myArcGISImageServiceLayer.NoDataColor = Colors.Black;
    
    //Option #2
    //Color? myNoDataColor = Color.FromArgb(0, 0, 0, 0);
    //myArcGISImageServiceLayer.NoDataColor = myNoDataColor;
    
    //Option #2a
    //Nullable<Color> myNoDataColor2 = Color.FromArgb(0, 0, 0, 0);
    //myArcGISImageServiceLayer.NoDataColor = myNoDataColor2;
  }
  else if (rb_Red.IsChecked == true)
  {
    // Since the color RED does not exactly match the NoDataColor defined in the ArcGIS Server ArcGISImageServiceLayer,
    // the NoData pixels will be displayed.
    //
    // The following three code-behind Options all produce the same result:
    
    //Option #1
    myArcGISImageServiceLayer.NoDataColor = Colors.Red;
    
    //Option #2
    //Color? myNoDataColor = Color.FromArgb(0, 255, 0, 0);
    //myArcGISImageServiceLayer.NoDataColor = myNoDataColor;
    
    //Option #2a
    //Nullable<Color> myNoDataColor2 = Color.FromArgb(0, 255, 0, 0);
    //myArcGISImageServiceLayer.NoDataColor = myNoDataColor2;
  }
  
  // Call the ArcGISImageServiceLayer.Refresh Method to force a round trip to the ArcGIS Server and display
  // the changes made to the ArcGISImageServiceLayer.NoDataColor values.
  myArcGISImageServiceLayer.Refresh();
}

' The following MSDN help documents provide more information on the System.Windows.Media.Color Structure:
' http://msdn.microsoft.com/en-us/library/system.windows.media.color(v=vs.95).aspx
' http://msdn.microsoft.com/en-us/library/system.windows.media.colors(v=vs.95).aspx
' 
' TIP:
' Use the Microsoft Calculator in the 'Programmer' mode see what a Dec and Hex equivalents are.
  
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs)
  
  ' Get the ArcGISImageServiceLayer defined in XAML.
  Dim myArcGISImageServiceLayer As ESRI.ArcGIS.Client.ArcGISImageServiceLayer = Map1.Layers(1)
  
  If rb_Black.IsChecked = True Then
    
    ' The NoData values that were defined in the ArcGIS Server ArcGISImageServiceLayer are BLACK. Only when
    ' the ArcGISImageServiceLayer.NoDataColor value exactly matches will the NoData pixels be displayed
    ' as transparent.
    '
    ' The following three code-behind Options all produce the same result:
    
    'Option #1
    myArcGISImageServiceLayer.NoDataColor = Colors.Black
    
    'Option #2
    'Dim myNoDataColor? As Color = Color.FromArgb(0, 0, 0, 0)
    'myArcGISImageServiceLayer.NoDataColor = myNoDataColor
    
    'Option #2a
    'Dim myNoDataColor2 As Nullable(Of Color) = Color.FromArgb(0, 0, 0, 0)
    'myArcGISImageServiceLayer.NoDataColor = myNoDataColor2
    
  ElseIf rb_Red.IsChecked = True Then
    
    ' Since the color RED does not exactly match the NoDataColor defined in the ArcGIS Server ArcGISImageServiceLayer,
    ' the NoData pixels will be displayed.
    '
    ' The following three code-behind Options all produce the same result:
    
    'Option #1
    myArcGISImageServiceLayer.NoDataColor = Colors.Red
    
    'Option #2
    'Dim myNoDataColor? As Color = Color.FromArgb(0, 255, 0, 0)
    'myArcGISImageServiceLayer.NoDataColor = myNoDataColor
    
    'Option #2a
    'Dim myNoDataColor2 As Nullable(Of Color) = Color.FromArgb(0, 255, 0, 0)
    'myArcGISImageServiceLayer.NoDataColor = myNoDataColor2
    
  End If
  
  ' Call the ArcGISImageServiceLayer.Refresh Method to force a round trip to the ArcGIS Server and display
  ' the changes made to the ArcGISImageServiceLayer.NoDataColor values.
  myArcGISImageServiceLayer.Refresh()
  
End Sub