App.xaml.cs

using System;
using Windows.ApplicationModel;
using Windows.ApplicationModel.Activation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Navigation;

namespace Xamarin.Forms.Sandbox.UWP
{
	sealed partial class App : global::Windows.UI.Xaml.Application
	{
		public App()
		{
			InitializeComponent();
			Suspending += OnSuspending;
		}

		protected override void OnLaunched(LaunchActivatedEventArgs e)
		{
			var rootFrame = Window.Current.Content as Windows.UI.Xaml.Controls.Frame;

			// Do not repeat app initialization when the Window already has content,
			// just ensure that the window is active
			if (rootFrame == null)
			{
				// Create a Frame to act as the navigation context and navigate to the first page
				rootFrame = new Windows.UI.Xaml.Controls.Frame();

				rootFrame.NavigationFailed += OnNavigationFailed;

				Xamarin.Forms.Forms.Init(e);

				if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
				{
					//TODO: Load state from previously suspended application
				}

				// Place the frame in the current Window
				Window.Current.Content = rootFrame;
			}

			if (rootFrame.Content == null)
			{
				// When the navigation stack isn't restored navigate to the first page,
				// configuring the new page by passing required information as a navigation
				// parameter
				rootFrame.Navigate(typeof(MainPage), e.Arguments);
			}
			// Ensure the current window is active
			Window.Current.Activate();
		}

		void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
		{
			throw new Exception("Failed to load Page " + e.SourcePageType.FullName);
		}

		private void OnSuspending(object sender, SuspendingEventArgs e)
		{
			var deferral = e.SuspendingOperation.GetDeferral();
			//TODO: Save application state and stop any background activity
			deferral.Complete();
		}
	}
}