ajax

 $("#dlProvince").change(function () {
             var id = document.getElementById("dlProvince").value;
             Load("SCity", id);
         });
         $("#SCity").change(function () {
             var sid = document.getElementById("SCity").value;
             Load("SSHI", sid);
         });

         function Load(obj, pid) {
             var url = "/WebUI/Admin/Benefit/Area.ashx?pid=" + pid + "&obj=" + obj;
             $.get(url, null, function (data) {
                 var jsonlist = eval(data);
                 for (var i = 0; i < jsonlist.length; i++) {
                     var op = new Option(jsonlist[i].Name, jsonlist[i].Id);
                     document.getElementById(obj).options.add(op);
                 }
             });
             //var xmlhttp = new XMLHttpRequest();
             //if (xmlhttp == null) {
             //    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
             //}
             
             //alert(url);
             //xmlhttp.open("GET", url, true);
             //xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
             //xmlhttp.onreadystatechange = function () {
             //    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
             //        document.getElementById(obj).innerHTML = "<option value='0'>-请选择-</option>";
             //        var jsonlist = eval(xmlhttp.responseText);
                    
             //        for (var i = 0; i < jsonlist.length; i++) {
             //            var op = new Option(jsonlist[i].Name, jsonlist[i].Id);
             //            document.getElementById(obj).options.add(op);
             //        }
             //    }
             //}
             //xmlhttp.send(null);
         }



//一般处理程序
 public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            string obj = context.Request.QueryString["obj"];
            string id = context.Request.QueryString["pid"];
            if (obj == "SCity")
            {
                SysLocation Location = new SysLocation();
                Location.AddCondition("Depth", 3);
                Location.AddCondition("Pid", id);
                IList<SysLocation> listCity = BDAContext.GetObject<ISysLocationBLL>().QueryPageList(Location, 1, int.MaxValue);
                string json = JsonConvert.SerializeObject(listCity);
                context.Response.Write(json);
            }
            else
            {

                SysLocation obje = new SysLocation();
                obje.AddCondition("Depth", 4);
                obje.AddCondition("Pid", id);
                IList<SysLocation> listDistrict = BDAContext.GetObject<ISysLocationBLL>().QueryPageList(obje, 1, int.MaxValue);
                string json = JsonConvert.SerializeObject(listDistrict);
                context.Response.Write(json);
            }


        }

//前台
             <Bda:SortableGridRow>
                                    <HeaderTemplate Width="150px">
                                地区<span style="color: #FF0000">*</span>
                                    </HeaderTemplate>
                                    <ItemTemplate>
                                   
                   <asp:DropDownList ID="dlProvince" runat="server" AutoPostBack="true" ClientIDMode="static" Height="25px" Width="30%"></asp:DropDownList>&nbsp;
                                        <select id="SCity"  ClientIDMode="static" runat="server" ><option value='0'>-请选择-</option></select>
                                        <select id="SSHI"  ClientIDMode="static" runat="server" ><option value='0'>-请选择-</option></select>
                   <%--<asp:DropDownList ID="dlCity" runat="server" AutoPostBack="true" ClientIDMode="static" Height="25px"  Width="30%"></asp:DropDownList>--%>&nbsp;
                    <%--<asp:DropDownList ID="ddlcounty" runat="server" Height="25px"  Width="30%"></asp:DropDownList>--%>&nbsp;
                  
                                <%--<asp:TextBox ID="Location" runat="server" CssClass="TextStyle validate[required,minSize[2]] text-input" Width="90%" MaxLength="20"></asp:TextBox>--%>
                                    </ItemTemplate>
                                </Bda:SortableGridRow>