public async Task <ActionResult> Create(PositionCreateViewModel model)
        {
            if (ModelState.IsValid)
            {
                var teachers = await UserManager.GetNoPositionTeachersAsync();

                ViewBag.selectListTeacher = new SelectList(teachers, "Id", "Name");

                var departs = await DepartmentManager.GetAllEntities().ToListAsync();

                ViewBag.selectListDepart = new SelectList(departs, "Id", "Name");

                var offices = await OfficeManager.GetOfficesForDepartment(departs.ElementAtOrDefault(0)).ToListAsync();

                ViewBag.selectListOffice = new SelectList(offices, "Id", "Name");

                var user = await UserManager.FindByIdAsync(model.UserId);

                if (user == null)
                {
                    ModelState.AddModelError("", "用户不存在");
                    return(View(model));
                }
                var office = await OfficeManager.FindEntityByIdAsync(model.OfficeId);

                if (office == null)
                {
                    ModelState.AddModelError("", "部门不存在");
                    return(View(model));
                }
                var position = new Position()
                {
                    Name        = model.Name,
                    Description = model.Description,
                    HeadUser    = user.TeacherInfo,
                    Office      = office
                };
                position = await PositionManager.AddEntityAsync(position);

                user.TeacherInfo.Position = position;
                await UserManager.UpdateAsync(user);

                return(RedirectToAction("Index"));
            }
            return(View(model));
        }