/// <summary>
 /// Handles the Click event on the setting app bar button, this displays the 
 /// <see cref="SettingsDialog"/> used to manage the Dropbox connection.
 /// </summary>
 /// <param name="sender">The sender.</param>
 /// <param name="args">The <see cref="RoutedEventArgs"/> instance containing the event data.</param>
 private async void SettingsClick(object sender, RoutedEventArgs args)
 {
     var settings = new SettingsDialog();
     var result = await settings.ShowAsync();
     if (result == ContentDialogResult.Primary)
     {
         var app = (App)Application.Current;
         if (string.IsNullOrEmpty(app.AccessToken))
         {
             DropboxOAuth.AuthorizeAndContinue();
         }
         else
         {
             app.AccessToken = string.Empty;
             this.NotConnected.Visibility = Visibility.Visible;
             this.RefreshButton.IsEnabled = false;
         }
     }
 }