public void AddToFavourites(Film film)
 {
     if (FavorieteFilms.Where(p => p.IsWatchlist).Select(f => f.Film).Contains(film))
     {
         CustomerFilm f2 = FavorieteFilms.FirstOrDefault(f => f.FilmId == film.Id);
         f2.IsWatchlist = false;
     }
     else
     {
         FavorieteFilms.Add(new CustomerFilm()
         {
             Film = film, FilmId = film.Id, Klant = this, CustomerId = this.CustomerId, IsWatchlist = false
         });
     }
 }
        public void RemoveFavourite(Film film)
        {
            CustomerFilm cf = FavorieteFilms.SingleOrDefault(f => f.FilmId == film.Id);

            FavorieteFilms.Remove(cf);
        }