public void EditDvd(Dvd dvd, int id)
        {
            DvdLibraryEFEntities db = new DvdLibraryEFEntities();

            dvd.DvdId = id;

            db.Dvds.AddOrUpdate(d => d.DvdId, dvd);

            db.SaveChanges();
        }
        public void DeleteDvd(int id)
        {
            DvdLibraryEFEntities db = new DvdLibraryEFEntities();

            var target = db.Dvds.Find(id);

            if (target != null)
            {
                db.Dvds.Remove(target);
            }

            db.SaveChanges();
        }
        public void AddDvd(Dvd dvd)
        {
            DvdLibraryEFEntities db = new DvdLibraryEFEntities();

            //IEnumerable<DbEntityValidationResult> validation = db.GetValidationErrors();

            bool valid = (dvd.Title != null &&
                          dvd.RealeaseYear > 0 &&
                          dvd.Director != null &&
                          dvd.Rating != null);

            //foreach (var v in validation)
            //{
            //    valid = v.IsValid;
            //}

            if (valid)
            {
                db.Dvds.AddOrUpdate(dvd);
                db.SaveChanges();
            }
        }