private void catalogueTabContentChangedEventHandler(object sender, RoutedEventArgs e) { if (titleTextBox.Text == "" && authorTextBox.Text == "" && publisherTextBox.Text == "" && selectedGenresList.Count == 0 && languageComboBox.SelectedIndex <= -1) { cashierCatalogue.ItemsSource = catalogue; } else { var title = titleTextBox.Text; var author = authorTextBox.Text; var publisher = publisherTextBox.Text; var language = languageComboBox.SelectedItem == null ? "" : languageComboBox.SelectedItem.ToString(); var genres = selectedGenresListBox.Items; cashierCatalogue.ItemsSource = new CatalogueViewList((List <Book>)bookChangeManager.bookBeingSearched(title, author, publisher, language, genres), dao.CachedBookstores, dao.CachedBookstoresOnBooksAvailability).list; } }