Public Property NoData As Nullable(Of Double)

public Nullable<double> NoData {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="-14553964,3695023,-11813724,5327601">
  
    <!-- Add an ArcGISTiledMapServiceLayer. -->
    <esri:ArcGISTiledMapServiceLayer ID="Topo" 
            Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer"/>
    
    <!-- 
    In order to have the NoData Property return an image where the NoData pixels are transparent the 
    ArcGISImageServiceLayer.ImageFormat must use a lossless compression. Valid lossless compression 
    types are: PNG24, PNG8, PNG32, and JPGPNG.
    
    NOTES:
    If you get the NoData pixel value wrong the NoData pixels still show but they will just not be transparent.
    -->
    
    <!-- NoData Property. -->
    <esri:ArcGISImageServiceLayer 
       Url="http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Earthquakes/CaliforniaDEM/ImageServer" 
       ImageFormat="PNG24" NoData="0" />
    
  </esri:Map>
  
  <!-- Add controls to demonstrate the effect of changing the ArcGISImageServiceLayer.NoData. -->
  <Button Content="Change NoData Pixel " Height="23" HorizontalAlignment="Left" Margin="12,84,0,0" 
          Name="Button1" VerticalAlignment="Top" Width="151" Click="Button1_Click"/>
  <RadioButton Content="Pixel=0" Height="16" HorizontalAlignment="Left" Margin="169,87,0,0" 
               Name="rb_Pixel_0" VerticalAlignment="Top" IsChecked="True" />
  <RadioButton Content="Pixel=19" Height="16" HorizontalAlignment="Left" Margin="249,87,0,0" 
               Name="rb_Pixel_19" 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 'Pixel=0' or 'Pixel=19' radio button and then click the 
             'Change NoData Pixel' button to see the effect of modifying the ArcGISImageServiceLayer.NoData 
             Property. By choosing the 'Pixel=0' radio button the NoData pixels will be made transparent. Setting 
             the NoData to any other pixel value other than what is defined in the ArcGIS Server map service as 
             the as the NoData pixel value will result in the NoData pixels being displayed." />
</Grid>

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_Pixel_0.IsChecked == true)
  {
    // The NoData pixel values that were defined in the ArcGIS Server ArcGISImageServiceLayer are 0. 
    // Only when the ArcGISImageServiceLayer.NoData value exactly matches will the NoData pixels be 
    // displayed as transparent.
    //
    // The following two code-behind Options produce the same result:
    
    //Option #1
    double? myNoData = 0;
    myArcGISImageServiceLayer.NoData = myNoData;
    
    //Option #2
    //Nullable<double> myNoData2 = 0;
    //myArcGISImageServiceLayer.NoData = myNoData2;
  }
  else if (rb_Pixel_19.IsChecked == true)
  {
    // Since the pixel value of 19 does not exactly match the NoData value defined in the ArcGIS Server 
    // ArcGISImageServiceLayer, the NoData pixels will be displayed.
    //
    // The following two code-behind Options produce the same result:
    
    //Option #1
    double? myNoData = 19;
    myArcGISImageServiceLayer.NoData = myNoData;
    
    //Option #2
    //Nullable<double> myNoData2 = 19;
    //myArcGISImageServiceLayer.NoData = myNoData2;
  }
  
  // Call the ArcGISImageServiceLayer.Refresh Method to force a round trip to the ArcGIS Server and display
  // the changes made to the ArcGISImageServiceLayer.NoData values.
  myArcGISImageServiceLayer.Refresh();
}

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_Pixel_0.IsChecked = True Then
    
    ' The NoData pixel values that were defined in the ArcGIS Server ArcGISImageServiceLayer are 0. 
    ' Only when the ArcGISImageServiceLayer.NoData value exactly matches will the NoData pixels be 
    ' displayed as transparent.
    '
    ' The following two code-behind Options produce the same result:
    
    'Option #1
    Dim myNoData? As Double = 0
    myArcGISImageServiceLayer.NoData = myNoData
    
    'Option #2
    'Dim myNoData2 As Nullable(Of Double) = 0
    'myArcGISImageServiceLayer.NoData = myNoData2
    
  ElseIf rb_Pixel_19.IsChecked = True Then
    
    ' Since the pixel value of 19 does not exactly match the NoData value defined in the ArcGIS Server 
    ' ArcGISImageServiceLayer, the NoData pixels will be displayed.
    '
    ' The following two code-behind Options produce the same result:
    
    'Option #1
    Dim myNoData? As Double = 19
    myArcGISImageServiceLayer.NoData = myNoData
    
    'Option #2
    'Dim myNoData2 As Nullable(Of Double) = 19
    'myArcGISImageServiceLayer.NoData = myNoData2
    
  End If
  
  ' Call the ArcGISImageServiceLayer.Refresh Method to force a round trip to the ArcGIS Server and display
  ' the changes made to the ArcGISImageServiceLayer.NoData values.
  myArcGISImageServiceLayer.Refresh()
  
End Sub