三级联动

 1 <h2>Index</h2>
 2 @*一级根节点*@
 3 @Html.DropDownList("YiJi", ViewBag.user as SelectList, new { onchange = "City()" })
 4 
 5 <select id="Select1" onchange="Citys()">
 6     <option>二级根节点</option>
 7 </select>
 8 
 9 
10 <select id="Select2">
11     <option>三级根节点</option>
12 </select>
13 
14 
15 <script>
16     //二级联动
17     function City() {
18         var i = $("#YiJi").val();
19         $.ajax({
20             url: "/Default/GetCity?id=" + i,
21             dataType: "json",
22             type: "get",
23             success: function (data) {
24                 $("#Select1").empty().append("<option >二级根节点</option>")
25                 $("#Select2").empty().append("<option >三级根节点</option>")
26                 $(data).each(function () {
27                     var str = '<option value="' + this.Id + '">' + this.Name + '</option>';
28                     $("#Select1").append(str);
29                 })
30             }
31         })
32 
33     }
34     //三级联动
35     function Citys() {
36         var i = $("#Select1").val();
37         $.ajax({
38             url: "/Default/GetCity?id=" + i,
39             dataType: "json",
40             type: "get",
41             success: function (data) {
42                 $("#Select2").empty().append("<option >三级根节点</option>")
43                 $(data).each(function () {
44                     var str = '<option value="' + this.Id + '">' + this.Name + '</option>';
45                     $("#Select2").append(str);
46                 })
47             }
48         })
49 
50     }
51 </script>

视图View

 CityBll bll = new CityBll();
        /// <summary>
        /// 主页面
        /// </summary>
        /// <returns></returns>
        public ActionResult Index()
        {
            var list = bll.getList().Where(m => m.PId == 0).ToList();
            SelectList list2 = new SelectList(list, "Id", "Name");
            ViewBag.user = list2;
            return View();
        }
        /// <summary>
        /// 获取城市信息
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public string GetCity(int id)
        {
            var list = bll.getList().Where(m => m.PId == id).ToList();
            return JsonConvert.SerializeObject(list);
        }

控制器