结合三层，使用存储过程与JQ实现下拉框的联动

前台代码略；

 JS端：

function createTag(parentTagId, childTag) {
    var thisObj = document.createElement(childTag);
    var parent = document.getElementById(parentTagId);
    parent.appendChild(thisObj); return thisObj;
    }

function FirstModel() {
    var FirstModel = $("#SelectFirst")[0].value;
    var Site = $("#seCompanyCode")[0].value;
    $.ajax({
        type: "get",
        cache: false,
        dataType: "Json",
        url: "../forms/handler/SecondModel.ashx",
        data: {
            FirstModel: FirstModel,
            Site: Site
        },
        beforeSend: function (XMLHttpRequest) { },
        success: function (data, textStatus) {
            if (data) {
                var selectSecond = $("#SelectSecond");
                selectSecond.empty();
                var jsonObject = eval(data.Table);
                for (var i = 0; i < jsonObject.length; i++) {
                    var createObj = createTag('SelectSecond', 'option');

                    createObj.value = jsonObject[i].numbers;
                    createObj.Text = jsonObject[i].notects;
                    createObj.innerText = jsonObject[i].notects;

                }

  
            }
        },
        complete: function (data, textStatus) { },
        error: function () { }
    });

}

ashx端：

    public string GetResult(HttpContext context) {

        System.Data.DataSet DS = new System.Data.DataSet();
         HttpRequest Request = context.Request;
         string firstModel = Request.QueryString["FirstModel"];
         string Site = Request.QueryString["Site"];
         ContractBLL bll = new ContractBLL();
         DS = bll.LoadSecodModel(firstModel,Site);
         return MyJson.DataTable2Json(DS.Tables[0]);
      
   
    }

CS端略