int movie_id = 100;
            var res = from mtg in db.MovieToGenres
                      join genre in db.Genres on mtg.genre_ID equals
                          genre.genre_ID
                      group genre.genre_string by mtg.movie_ID
                      into gs where gs.Key == movie_id select gs;
            List<string> genre_strings_for_one_movie = res.First().ToList();