protected override void OnNavigatedFrom(NavigationEventArgs e)
 {
     try
     {
         if (e.NavigationMode == NavigationMode.Back)
         {
             _previousIndex = 0;
             if (_articleViewModel != null)
             {
                 ApplicationBar.IsVisible = false;
                 _articleViewModel.ClearArticle();
             }
         }
         base.OnNavigatedFrom(e);
     }
     catch (Exception exception)
     {
         if (Debugger.IsAttached)
         {
             Debug.WriteLine("ArticlePage.xaml.cs:" + exception);
         }
     }
 }