public ActionResult AddPerformer(long id)
        {
            if (!db.Teams.Any(x => x.Id == id))
            {
                return(HttpNotFound());
            }

            var model = new AddPerformerTeamViewModel();

            return(View(model));
        }
        public ActionResult AddPerformer(long id, AddPerformerTeamViewModel model)
        {
            var team = db.Teams.Find(id);

            if (model == null || team == null)
            {
                return(new HttpStatusCodeResult(HttpStatusCode.BadRequest));
            }

            if (!ModelState.IsValid)
            {
                return(RedirectToAction("Edit", new { id }));
            }

            var performer  = db.Users.Find(model.PerformerId);
            var constained = team.Performers.Any(x => x.Id == model.PerformerId);

            if (performer != null && !constained)
            {
                team.Performers.Add(performer);
                db.SaveChanges();
            }
            return(RedirectToAction("Edit", new { id }));
        }