public sealed class Legend : MapSurround, System.ComponentModel.INotifyPropertyChanged, System.IComparable, System.IEquatable<Element>  

//Create a legend for an associated map frame.

//Construct on the worker thread
await QueuedTask.Run(() =>
{
  //Build 2D envelope geometry
  Coordinate2D leg_ll = new Coordinate2D(6, 2.5);
  Coordinate2D leg_ur = new Coordinate2D(8, 4.5);
  Envelope leg_env = EnvelopeBuilder.CreateEnvelope(leg_ll, leg_ur);

  //Reference MF, create legend and add to layout
  MapFrame mapFrame = layout.FindElement("New Map Frame") as MapFrame;
  if (mapFrame == null)
  {
    ArcGIS.Desktop.Framework.Dialogs.MessageBox.Show("Map frame not found", "WARNING");
    return;
  }
  Legend legendElm = LayoutElementFactory.Instance.CreateLegend(layout, leg_env, mapFrame);
  legendElm.SetName("New Legend");
});