public override Task OnNavigatedToAsync(object parameter, NavigationMode mode, IDictionary<string, object> state)
 {
     if (state.ContainsKey(nameof(Image)))
     {
         Image = state[nameof(Image)] as BingImage;
         state.Clear();
     }
     else
     {
         Image = parameter as BingImage;
     }
     return Task.CompletedTask;
 }
 public void GotoDetailsPage(BingImage image)
 {
     NavigationService.Navigate(typeof(Views.DetailPage), image);
 }