public ActionResult Edit(string UserName)
        {
            var tum = tub.GetTeacherUserModel(UserName);

            if (tum != null)
            {
                ViewBag.TeacherID = new SelectList(tb.GetTeachers(), "ID", "TeacherName", tum.TeacherID);
                return(View(tum));
            }
            else
            {
                return(RedirectToAction("Index"));
            }
        }
        /// <summary>
        /// 验证用户名是否存在
        /// </summary>
        /// <param name="UserName">传过来的用户名</param>
        /// <returns></returns>
        public ActionResult ValidateUserName(string UserName)
        {
            var tum      = tub.GetTeacherUserModel(UserName);
            var teavalue = tum == null ? false : true;
            var stuvalue = sb.ValidateStuUserName(UserName);

            if (teavalue || stuvalue)
            {
                return(new JsonResult {
                    Data = true, JsonRequestBehavior = JsonRequestBehavior.AllowGet
                });
            }
            else
            {
                return(new JsonResult {
                    Data = false, JsonRequestBehavior = JsonRequestBehavior.AllowGet
                });
            }
        }