public ActionResult Create(CourseAssign courseAssign)
        {
            if (ModelState.IsValid)
            {
                bool IsSaved = _courseAssignManager.Add(courseAssign);
                if (IsSaved)
                {
                    ViewBag.Message = "Assign Successfully";
                }
                else
                {
                    ViewBag.Message = "Asasign Failed";
                }
            }
            ViewBag.DepartmentId = new SelectList(_departmentManager.GetAll(), "Id", "Name");
            var defaultSelectListItem = new List <SelectListItem>()
            {
                new SelectListItem()
                {
                    Value = "", Text = "Select"
                }
            };

            ViewBag.CourseId  = defaultSelectListItem;
            ViewBag.TeacherId = defaultSelectListItem;
            return(View());
        }