private void AddFavoriteMovie(object sender, RoutedEventArgs e)
        {
            var selectedItem = SearchListBox.SelectedItem;

            if (selectedItem != null)
            {
                _userViewModel.AddFavoriteMovie();
                LoadMovies();
            }
            else
            {
                Window popup = new Window();
                popup.Title   = "Warning!";
                popup.Width   = 300;
                popup.Height  = 150;
                popup.Content = "\n\n\n \t Select a movie!";
                popup.ShowDialog();
            }
        }