public override string ToJson( 
   JsonSerializationSettings settings
)

{
  // Note: must be called on the QueuedTask
  {
    //Place a multipoint graphic using the mapview extent geometry
    var extent = MapView.Active.Extent;
    //Contract the extent
    var polygonEnv = extent.Expand(-100000, -90000, false);
    //create a polygon using the envelope
    var polygon = PolygonBuilderEx.CreatePolygon(polygonEnv);
    //Create MultipPoints from the polygon
    var multiPoints = MultipointBuilderEx.CreateMultipoint(polygon);
    //specify a symbol
    var point_symbol = SymbolFactory.Instance.ConstructPointSymbol(
                          ColorFactory.Instance.GreenRGB);
    //create a CIMGraphic 
    var graphic = new CIMMultipointGraphic
    {
      Symbol = point_symbol.MakeSymbolReference(),
      Multipoint = multiPoints
    };
    graphicsLayer.AddElement(graphic);
  }
}