XamarinForms orientation with UIInterfaceOrientationMask

		public override UIInterfaceOrientationMask GetSupportedInterfaceOrientations(UIApplication application, UIWindow forWindow)
		{
			if (Xamarin.Forms.Application.Current == null || Xamarin.Forms.Application.Current.MainPage == null)
			{
				return UIInterfaceOrientationMask.Portrait;
			}

			var navigationPage = Xamarin.Forms.Application.Current.MainPage as NavigationPage;


			var orientationPage = navigationPage.CurrentPage as ISupportOrientation;

			if (orientationPage != null)
			{
				UIInterfaceOrientationMask supportedMask = new UIInterfaceOrientationMask();

				foreach (var orientation in orientationPage.SupportedOrientation)
				{
					switch (orientation)
					{
						case DeviceOrientations.Portrait:
							supportedMask |= UIInterfaceOrientationMask.Portrait;
							break;

						case DeviceOrientations.Landscape:
							supportedMask |= UIInterfaceOrientationMask.Landscape;
							break;


						default:
							break;
					}
				}

				return supportedMask;
			}

			return UIInterfaceOrientationMask.Portrait;
		}
	}