private void OnNavigated(object sender, NavigationEventArgs args)
        {
            EventHandler <INavigationService, NavigationEventArgsBase> handler = Navigated;

            if (handler == null)
            {
                return;
            }
#if WINDOWS_PHONE
            args.SetHandled(true);
            args.InvokeAfterRestoreState(eventArgs => handler(this, new NavigationEventArgsWrapper(eventArgs)));
#else
            handler(this, new NavigationEventArgsWrapper(args));
#endif
        }