private void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
        {
            object navigationParameter;
            if (e.PageState != null && e.PageState.ContainsKey("SelectedItem"))
            {
                navigationParameter = e.PageState["SelectedItem"];
            }

            // TODO: Assign a bindable group to this.DefaultViewModel["Group"]
            // TODO: Assign a collection of bindable items to this.DefaultViewModel["Items"]
            // TODO: Assign the selected item to this.flipView.SelectedItem
        }
 /// <summary>
 /// Populates the page with content passed during navigation.  Any saved state is also
 /// provided when recreating a page from a prior session.
 /// </summary>
 /// <param name="sender">
 /// The source of the event; typically <see cref="NavigationHelper"/>
 /// </param>
 /// <param name="e">Event data that provides both the navigation parameter passed to
 /// <see cref="Frame.Navigate(Type, Object)"/> when this page was initially requested and
 /// a dictionary of state preserved by this page during an earlier
 /// session.  The state will be null the first time a page is visited.</param>
 private void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
 {
     // TODO: Assign a bindable collection of items to this.DefaultViewModel["Items"]
 }