页面2级分类

 public ActionResult Form(int? id) 
        {
            QueryType();
            EntryModel model = new EntryModel();
            if (id != null)
            {
                model = business.Get(id.Value);
            }
            return View(model);
        }

        private void QueryType()
        {
            EntryTypeRepository rep = new EntryTypeRepository();
            var list = rep.QueryByParentId(0);
            var select = new List<SelectListItem>();
            foreach (var item in list)
            {
                select.Add(new SelectListItem() { Text=item.Name,Value = item.Id.ToString()});
            }
            ViewBag.TypeList = select;
        }

        public ActionResult GetSecondType(int id = 0)
        {
            var list = new List<EntryTypeModel>();
            if (id != 0)
            {
                EntryTypeRepository rep = new EntryTypeRepository();
                list = rep.QueryByParentId(id);
            }
            else{
                list = new List<EntryTypeModel>();
            }
            return Json(list, JsonRequestBehavior.AllowGet);
        }

        [HttpPost]
        public ActionResult Form(EntryModel model)
        {
            if (ModelState.IsValid)
            {
                if (model.Id == 0)
                {
                    business.Add(model);
                }
                else
                {
                    business.Update(model.Id,model);
                }
            }
            return RedirectToAction("List");        
        }

  <li>
    @Html.LabelFor(m => m.TypeId)
      @Html.DropDownList("Parent", ViewBag.TypeList as List<SelectListItem>, new { onchange = "GetTypeByParentID(this)" })
      子类：<select id="TypeId" name="TypeId" style="100px;">
    <option value="0">请选择子类</option>
  </select>
    @Html.ValidationMessageFor(m => m.TypeId)

<script type="text/javascript">
    $(function () {
        GetTypeByParentID($("#Parent"));
    });
    function GetTypeByParentID(id) {
        $("#TypeId").empty();
        $.ajax({
            url: '/Entry/GetSecondType/' + $("#Parent").val(),
            type: "get",
            datatype: "json",
            success: function (data) {
                if (data.length == 0) {
                    $("<option></option>")
                    .val("0")
                    .text("请选择子类")
                    .appendTo($("#TypeId"));
                }
                $.each(data, function (i, item) {
                    $("<option></option>")
                    .val(item["Id"])
                    .text(item["Name"])
                    .appendTo($("#TypeId"));
                });
            }
        });
    }
</script>