public ActionResult Delete(int id)
        {
            using (TaskAllocationDBContext ctx = new TaskAllocationDBContext())
            {
                var user = ctx.Users.Where(u => u.Id == id).FirstOrDefault();
                if (user != null)
                {
                    ctx.Entry<User>(user).State = EntityState.Deleted;
                }
                else
                {
                    throw new Exception("user id is not exist:" + id);
                }

                ctx.SaveChanges();
            }

            return SuccessMessage(BasicMessage.DeleteSuccess);
        }