public static IDisposable AddOverlay( 
   MapView mapView,
   CIMGraphic graphic,
   double referenceScale
)

{
  // get the current MapView and point
  var myextent = mapView.Extent;
  var point = myextent.Center;
  IDisposable _graphic = null;

  // add point graphic to the overlay at the center of the mapView
  // Note: Needs QueuedTask to run
  _graphic = mapView.AddOverlay(point,
      SymbolFactory.Instance.ConstructPointSymbol(
              ColorFactory.Instance.RedRGB, 30.0, SimpleMarkerStyle.Star).MakeSymbolReference());

  // update the overlay with new point graphic symbol
  MessageBox.Show("Now to update the overlay...");
  // Note: Needs QueuedTask to run
  {
    mapView.UpdateOverlay(_graphic, point, SymbolFactory.Instance.ConstructPointSymbol(
                                  ColorFactory.Instance.BlueRGB, 20.0, SimpleMarkerStyle.Circle).MakeSymbolReference());
  }

  // clear the overlay display by disposing of the graphic
  MessageBox.Show("Now to clear the overlay...");
  _graphic.Dispose();
}

{
  // Use SourceURL for the URL to the image content. For
  // a local file, use a file path. For a web/internet file
  // location, use its URL
  //
  // Supported image types are:
  // png, jpg, tiff, bmp, gif, svg

  var pictureGraphic = new CIMPictureGraphic
  {
    SourceURL = @"C:\Images\MyImage.png",
    Shape = envelope
  };

  IDisposable _graphic = mapView.AddOverlay(pictureGraphic);
}

{
  IDisposable _graphic = null;

  //define the text symbol
  var textSymbol = new CIMTextSymbol();
  //define the text graphic
  var textGraphic = new CIMTextGraphic();

  // Note: Needs QueuedTask to run
  {
    //Create a simple text symbol
    textSymbol = SymbolFactory.Instance.ConstructTextSymbol(ColorFactory.Instance.BlackRGB, 8.5, "Corbel", "Regular");
    //Sets the geometry of the text graphic
    textGraphic.Shape = geometry;
    //Sets the text string to use in the text graphic
    textGraphic.Text = "This is my line";
    //Sets symbol to use to draw the text graphic
    textGraphic.Symbol = textSymbol.MakeSymbolReference();
    //Draw the overlay text graphic
    _graphic = MapView.Active.AddOverlay(textGraphic);
  }
}