void ImageEventsListPage_Loaded(object sender, RoutedEventArgs e)
        {

            _progressIndicator = new ProgressIndicator();
            _progressIndicator.IsVisible = true;
            SystemTray.ProgressIndicator = _progressIndicator;

            model = new EventsListViewModel();
            model.Category = Category;
            model.Load();

            _progressIndicator.IsVisible = false;
            this.DataContext = model;
        }
        protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);

            if (!PhoneApplicationService.Current.State.ContainsKey("ListEvents"))
            {
                MessageBox.Show("Il n'y pas de données présentes");
                NavigationService.GoBack();
                return;
            }

            model = PhoneApplicationService.Current.State["ListEvents"] as EventsListViewModel;
        }