// GET: Physicians/Create
        public ActionResult Create()
        {
            // Only users who aren't already Physicians can be registered as Physicians
            SelectList users      = new SelectList(db.AppUsers, "AppUserID", "Username");
            SelectList physicians = new SelectList(db.Physicians, "PhysicianID", "PhysicianID");

            var list = users.Where(u => physicians.All(p => p.Value != u.Value));

            ViewBag.PhysicianID = list;
            return(View());
        }