public MainPage() {
   this.InitializeComponent();
   _navigationHelper = new NavigationHelper(this);
   _navigationHelper.LoadState += navigationHelper_LoadState;
   _navigationHelper.SaveState += navigationHelper_SaveState;
 }
 public ProfilePage() {
   InitializeComponent();
   navigationHelper = new NavigationHelper(this);
   navigationHelper.LoadState += navigationHelper_LoadState;
   navigationHelper.SaveState += navigationHelper_SaveState;
 }