NullReferenceException on FirstorDefault()

 var db = new DatabaseContext();

                var staffMembers = db.StaffMember; // here i get right item 100%
                var temp = staffMembers.Where(x => x.Id == args.User.Id).ToList(); // <-- this returns me my item
                var staffMember = temp.FirstOrDefault(); // <-- System.NullReferenceException
                var stafftemp = temp[0]; // <-- null without any reason