Segurança Xamarin

AppDelegate.cs

public partial class AppDelegate : UIApplicationDelegate
	{
		NSObject _screenshotNotification = null;

		public override void OnActivated (UIApplication application)
		{
			 // Inicia a verificação
			    if (_screenshotNotification == null)
			    {
				_screenshotNotification = UIApplication.Notifications.ObserveUserDidTakeScreenshot((sender, args) =>
				{
				    Console.WriteLine("Usuario tirou foto");
				    Console.WriteLine("Notification: {0}", args.Notification);
				});
			    }
		}

		public override void OnResignActivation (UIApplication application)
		{
	            // Para a notificação
		    if (_screenshotNotification != null)
		    {
			_screenshotNotification.Dispose();
			_screenshotNotification = null;
		    }
		}
	}