public override void ViewDidLoad()
        {
            Title = "Home";

            // A 'view' aka label control for this view
            UILabel label = new UILabel();
            label.Text = "HomeViewController";
            label.Frame = Center(100,100);
            label.BackgroundColor = UIColor.LightGray;
            View.AddSubview(label);

            // 2 toolbar items
            UIBarButtonItem item1 = new UIBarButtonItem();
            item1.Title = "Click me";
            item1.Clicked += delegate(object sender, EventArgs e) {
                Level2ViewController controller = new Level2ViewController();
                NavigationController.PushViewController(controller,true);
            };

            UIBarButtonItem item2 = new UIBarButtonItem();
            item2.Title = "View with no back";
            item2.Clicked += delegate(object sender, EventArgs e) {
                ViewWithNoBackController controller = new ViewWithNoBackController();
                NavigationController.PushViewController(controller,true);
            };

            ToolbarItems = new UIBarButtonItem[] {item1,item2};

            base.ViewDidLoad ();
        }
        //        public override void ViewDidLoad ()
        //        {
        //            _firstController = new HomeViewController();
        //            PushViewController(_firstController,true);
        //            
        //            base.ViewDidLoad ();
        //        }
        public override void ViewDidLoad()
        {
            var firstController = new HomeViewController();
            var secondController = new Level2ViewController();
            var thirdController = new Level3ViewController();

            var viewControllers = ViewControllers.ToList();
            viewControllers.Add(firstController);
            viewControllers.Add(secondController);
            viewControllers.Add(thirdController);
            ViewControllers = viewControllers.ToArray();

            base.ViewDidLoad ();
        }