public SettingsPage()
        {
            this.InitializeComponent();

            this.navigationHelper = new NavigationHelper(this);
            this.navigationHelper.LoadState += this.NavigationHelper_LoadState;
            this.navigationHelper.SaveState += this.NavigationHelper_SaveState;
        }
        public MainPage()
        {
            InitializeComponent();

            navigationHelper = new NavigationHelper(this);
            navigationHelper.LoadState += navigationHelper_LoadState;
            navigationHelper.SaveState += navigationHelper_SaveState;

            NavigationCacheMode = NavigationCacheMode.Required;
        }