jquery通过json获取数据

<script type="text/javascript">
        $(document).ready(function () {
            getScatalog("paidang", "M06");

         });

function getScatalog(selectid,BaseCode) {
           if (BaseCode != "") {
               $.ajax({
                   url: "ajax/getCatalogByBasecode.aspx",
                   data: "code=" + encodeURI(BaseCode), cache: false,
                   datatype: "html",
                   success: function (context) {
                       fillselect(selectid, context);
                   }
               });
           }
           else {
               return "Error";
           }
       }

function fillselect(selectid, context) {
           var listitem=new Array();
           listitem = eval(context);
           for (var i = 0; i < listitem.length; i++) {
               $("#" + selectid).append("<option value='" + listitem[i]["code"] + "'>" + listitem[i]["name"] + "</option>");  //为Select追加一个Option(下拉项)
           }
       }

</script>

html代码：

<select id="paidang" class="selectstyle" name="paidang">
                  <option value="" selected>==请选择==</option>
              </select>

Ajax：

新建一个.aspx页面删除.aspx页面里的html代码删除，在.aspx.cs里添加如下代码

string rq_basecode=null;
       rq_basecode = Request.QueryString["code"];
       if (string.IsNullOrWhiteSpace(rq_basecode))
       {
           Response.Write("Error");
           Response.End();
       }

       BLLCataLog bll_info = new BLLCataLog();
       List<Scatalog> lt_info = new List<Scatalog>();
       lt_info = bll_info.GetCatalog(rq_basecode,"");
       //Response.Write(rq_basecode);
       if (lt_info.Count > 0)
       {
           Response.Write(JsonHelper.ToJson(lt_info));
       }
       else
       {
           Response.Write("Null");
       }

BLL层的数据：

public List<M2Model.Scatalog> GetCatalog(string code, string refcode)
       {
           DALCataLog dalcatalog6 = new M2SharpDAL.DALCataLog();
           return dalcatalog6.GetCatalog(code, refcode);
       }