Public ReadOnly Property ObjectIdField As String

public string ObjectIdField {get;}

private void MainPage_Loaded(object sender, System.Windows.RoutedEventArgs e)
{
  
  // The Map1 object (a Map object) was defined previously in XAML.
  
  // Create an ArcGISImageServiceLayer.
  ESRI.ArcGIS.Client.ArcGISImageServiceLayer myArcGISImageServiceLayer = new ESRI.ArcGIS.Client.ArcGISImageServiceLayer();
  myArcGISImageServiceLayer.Url = "http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Portland/CascadeLandsat/ImageServer";
            
  // Create an Event Handler.
  myArcGISImageServiceLayer.Initialized += new System.EventHandler<EventArgs>(ArcGISImageServiceLayer_Intialized);
                 
  // Add the ArcGISImageServiceLayer to the LayerCollection of the Map.
  Map1.Layers.Add(myArcGISImageServiceLayer);
                 
}
                 
private void ArcGISImageServiceLayer_Intialized(object sender, EventArgs e)
{
                 
  // The Map1 object (a Map object) and TextBlock_ObjectIdField (a TextBlock object) were defined previously in XAML.
                 
  // Access a specific ArcGISImageServiceLayer.
  ESRI.ArcGIS.Client.ArcGISImageServiceLayer myArcGISImageServiceLayer = (ESRI.ArcGIS.Client.ArcGISImageServiceLayer)Map1.Layers[0];
  
  // ObjectIdField Property (Read Only).
  TextBlock_ObjectIdField.Text = myArcGISImageServiceLayer.ObjectIdField;
                 
}

Private Sub MainPage_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded
                 
  ' The Map1 object (a Map object) was defined previously in XAML.
                 
  ' Create an ArcGISImageServiceLayer.
  Dim myArcGISImageServiceLayer As New ESRI.ArcGIS.Client.ArcGISImageServiceLayer
  myArcGISImageServiceLayer.Url = "http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Portland/CascadeLandsat/ImageServer"
                 
  ' Create an Event Handler.
  AddHandler myArcGISImageServiceLayer.Initialized, AddressOf ArcGISImageServiceLayer_Intialized
                 
  ' Add the ArcGISImageServiceLayer to the LayerCollection of the Map.
  Map1.Layers.Add(myArcGISImageServiceLayer)
                 
End Sub
                 
Private Sub ArcGISImageServiceLayer_Intialized(ByVal sender As Object, ByVal e As EventArgs)
                 
  ' The Map1 object (a Map object) and TextBlock_ObjectIdField (a TextBlock object) were defined previously in XAML.
                 
  ' Access a specific ArcGISImageServiceLayer.
  Dim myArcGISImageServiceLayer As ESRI.ArcGIS.Client.ArcGISImageServiceLayer = Map1.Layers.Item(0)
  
  ' ObjectIdField Property (Read Only).
  TextBlock_ObjectIdField.Text = myArcGISImageServiceLayer.ObjectIdField
                 
End Sub