public class Progressor 

public async Task Progressor_NonCancelable()
{
  ArcGIS.Desktop.Framework.Threading.Tasks.ProgressorSource ps = new ArcGIS.Desktop.Framework.Threading.Tasks.ProgressorSource("Doing my thing...", false);

  int numSecondsDelay = 5;
  //If you run this in the DEBUGGER you will NOT see the dialog
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() => Task.Delay(numSecondsDelay * 1000).Wait(), ps.Progressor);
}