UIViewController abstract baseclass for registering/unregistering for C# events according to the UIViewController's life-cycle. Refs: - http://stackoverflow.com/questions/15076905/weak-event-pattern-in-monotouch - http://stackoverflow.com/questions/1816614/viewwilldisappear-determine-whether-view-controller-is-being-popped-or-is-showi

gistfile1.cs

namespace BaseViewController
{
  public abstract class BaseViewController : ViewController
	{

		#region Actions / Events handling

		protected abstract void RegisterForActionsAndEvents ();
		protected abstract void UnregisterForActionsAndEvents ();

		public override void ViewWillAppear (bool animated)
		{
			base.ViewWillAppear (animated);

			if (!registeredForActionsAndEvents) {
				RegisterForActionsAndEvents ();
				registeredForActionsAndEvents = true;
			}
		}

		public override void ViewWillDisappear (bool animated)
		{
			base.ViewWillDisappear (animated);			

			bool shouldUnregister = false;

			if (registeredForActionsAndEvents) {

				if (NavigationController != null) {

					List<UIViewController> viewControllers = NavigationController.ViewControllers.ToList ();
					if (!viewControllers.Contains (this)) {

						// View is disappearing because it was popped from the navigation stack
						shouldUnregister = true;
					} else if (viewControllers.Count == 1 && PresentedViewController == null) {
            
						// View is disappearing because the whole navigation stack is being removed
						shouldUnregister = true;
					}
				} else {

					// View is disappearing (without being contained in a navigation stack)
					shouldUnregister = true;
				}
			}

			if (shouldUnregister) {
				UnregisterForActionsAndEvents ();
				registeredForActionsAndEvents = false;
			}
		}

		bool registeredForActionsAndEvents;

		#endregion
	}
}