Helper for displaystack in ios

DisplayStack.cs

using System;
using MonoTouch.UIKit;
using System.Collections.Generic;
using FdvWeb.Core;

namespace FdvWeb
{
	public class DisplayStack
	{
		readonly UITabBarController root;
		readonly Stack<UIViewController> modalStack;
		public DisplayStack (UITabBarController root)
		{
			this.root = root;
			this.modalStack = new Stack<UIViewController> ();
		}
		
		public void ShowModal (UIViewController viewController, bool animated = true)
		{
			Util.RunOnUIThread (delegate {
				if (modalStack.Count == 0)
					root.PresentModalViewController (viewController, animated);
				else
					modalStack.Peek ().PresentModalViewController (viewController, animated);
				
				modalStack.Push (viewController);
			});
		}
		
		public void DismissModal (bool animated = true)
        {
            modalStack.Pop ();
				
            IoCContainer.Current.Resolve<IUIThreadDispatcher> ().RunLater (delegate {
                if (modalStack.Count == 0)
                    root.DismissModalViewControllerAnimated (animated);
                else
                    modalStack.Peek ().DismissModalViewControllerAnimated (animated);
            });
        }
		
		public void PushView (UIViewController viewController, bool animated = true)
		{
			Util.RunOnUIThread (delegate {
				UINavigationController navController;
				if (modalStack.Count == 0) 
					navController = root.SelectedViewController as UINavigationController;
				else
					navController = modalStack.Peek () as UINavigationController;
				
				if (navController == null) 
					throw new InvalidOperationException ("Can only push on a navigation-controller");
				
				navController.PushViewController (viewController, animated);
			});
		}
		
		public void PopView (bool animated = true)
		{
			Util.RunOnUIThread (delegate {
				UINavigationController navController;
				if (modalStack.Count == 0) 
					navController = root.SelectedViewController as UINavigationController;
				else
					navController = modalStack.Peek () as UINavigationController;
				
				if (navController == null) 
					throw new InvalidOperationException ("Can only pop on a navigation-controller");
				
				navController.PopViewControllerAnimated (animated);
			});
		}
		
		public void PopToView (UIViewController viewController, bool animated = true)
		{
			Util.RunOnUIThread (delegate {
				UINavigationController navController;
				if (modalStack.Count == 0) 
					navController = root.SelectedViewController as UINavigationController;
				else
					navController = modalStack.Peek () as UINavigationController;
				
				if (navController == null) 
					throw new InvalidOperationException ("Can only pop on a navigation-controller");
				
				navController.PopToViewController (viewController, animated);
			});
		}
		
		public void PopToRoot (bool animated = true)
        {
            Util.RunOnUIThread (delegate {
                UINavigationController navController;
                if (modalStack.Count == 0) 
                    navController = root.SelectedViewController as UINavigationController;
                else
                    navController = modalStack.Peek () as UINavigationController;
				
                if (navController == null) 
                    throw new InvalidOperationException ("Can only pop on a navigation-controller");
				
                navController.PopToRootViewController (animated);
            });
        }

        public UIViewController TopViewController
        {
            get
            {
                UIViewController ret = null;
                Util.RunOnUIThread (delegate {
                    UIViewController vc;
                    UINavigationController navController;
                    if (modalStack.Count == 0) 
                        vc = root;
                    else
                        vc = modalStack.Peek ();

                    if (vc is UINavigationController) {
                        navController = (UINavigationController)vc;
                        ret = navController.ViewControllers[navController.ViewControllers.Length - 1];
                    } else {
                        ret = vc;
                    }
                });
                return ret;
            }
        }
	}
}

extensionmethods.cs

	public static class ExtensionMethods
	{
		public static UINavigationController Wrap (this DialogViewController dvc)
		{
			return new UINavigationController (dvc);
		}
	}