void BtnAddFavorite_Click(object sender, RoutedEventArgs e) { if (PopupFavorite.IsOpen && PopupFavorite.DataContext is Favorite) { var fav = (Favorite)PopupFavorite.DataContext; Favorites.List.Add(fav); try { Favorites.Save(); } catch (Exception ex) { MessageBox.Show(this, ex.Message, Title, MessageBoxButton.OK, MessageBoxImage.Error); } PopupFavorite.IsOpen = false; PopupFavorite.DataContext = null; } }