public class MapViewOverlayControl : IMapViewOverlayControl, System.ComponentModel.INotifyPropertyChanged  

//Creat a Progress Bar user control
var progressBarControl = new System.Windows.Controls.ProgressBar();
//Configure the progress bar
progressBarControl.Minimum = 0;
progressBarControl.Maximum = 100;
progressBarControl.IsIndeterminate = true;
progressBarControl.Width = 300;
progressBarControl.Value = 10;
progressBarControl.Height = 25;
progressBarControl.Visibility = System.Windows.Visibility.Visible;
//Create a MapViewOverlayControl. 
var mapViewOverlayControl = new MapViewOverlayControl(progressBarControl, true, true, true, OverlayControlRelativePosition.BottomCenter, .5, .8);
//Add to the active map
MapView.Active.AddOverlayControl(mapViewOverlayControl);
await QueuedTask.Run(() =>
{
  //Wait 3 seconds to remove the progress bar from the map.
  Thread.Sleep(3000);

});
//Remove from active map
MapView.Active.RemoveOverlayControl(mapViewOverlayControl);