gistfile1.txt

nint taskId = -1;
		Task savingChoiceTask;

		public async override void DidEnterBackground (UIApplication app)
		{
			Logger.Log ("DidEnterBackground() - entered background");

			// Begin Finite-Length Task.
			this.taskId = app.BeginBackgroundTask (null);

			// Start saving the user choices.
			// Note that the method will by default execute on the UI thread. If you go back to the app while the method
			// is running, you won't see any UI updates and the app will eventually crash. That's why we run it on a separate thread.
			if (savingChoiceTask == null || savingChoiceTask.IsCompleted) {
				savingChoiceTask = Task.Run (() => this.SaveUserChoices ());
				await savingChoiceTask;
			}

			// End Finite-Length Task, finished.
			if (this.taskId != -1)
			{
				UIApplication.SharedApplication.EndBackgroundTask (this.taskId);
				this.taskId = -1;
			}
		}