三级联动

<h2>Index</h2>
@*一级根节点*@
@Html.DropDownList("YiJi", ViewBag.user as SelectList, new { onchange = "City()" })

<select id="Select1" onchange="Citys()">
    <option>二级根节点</option>
</select>


<select id="Select2">
    <option>三级根节点</option>
</select>


<script>
    //二级联动
    function City() {
        var i = $("#YiJi").val();
        $.ajax({
            url: "/Default/GetCity?id=" + i,
            dataType: "json",
            type: "get",
            success: function (data) {
                $("#Select1").empty().append("<option >二级根节点</option>")
                $("#Select2").empty().append("<option >三级根节点</option>")
                $(data).each(function () {
                    var str = '<option value="' + this.Id + '">' + this.Name + '</option>';
                    $("#Select1").append(str);
                })
            }
        })

    }
    //三级联动
    function Citys() {
        var i = $("#Select1").val();
        $.ajax({
            url: "/Default/GetCity?id=" + i,
            dataType: "json",
            type: "get",
            success: function (data) {
                $("#Select2").empty().append("<option >三级根节点</option>")
                $(data).each(function () {
                    var str = '<option value="' + this.Id + '">' + this.Name + '</option>';
                    $("#Select2").append(str);
                })
            }
        })

    }
</script>

 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);
        }