public ActionResult PageDetail()
{
  var thisList = _sysDepartmentBll.GetAllDepartmentList();//数据源
  //添加一条默认数据
  var resultList = new List<SelectListItem>
  {
    new SelectListItem {Text = "--请选择--", Selected = true, Value = ""}
  };
  //将数据源添加到resultList集合中
  resultList.AddRange(thisList.Select(thisModel => new SelectListItem
  {
    Text = thisModel.DepartmentName,
    Selected = false,
    Value = thisModel.DepartmentId
  }));
  ViewBag.DepartmentList= GetDepartmentSelectList(_sysDepartmentBll.GetAllDepartmentList());
  return View();
}