How Can I Pass Arguments In Jqxgrid To Bind

<script type="text/javascript">
        function ADD2Grid() {
            //Getting the source data with ajax GET request
            var tt = $('#ddltitle :selected').text() + "|" +
                $("#<%=txtfn.ClientID %>").val() + "|" +
                $("#<%=txtmn.ClientID %>").val() + "|" +
                $("#<%=txtln.ClientID %>").val();
            //alert(tt);
            source = {
                datatype: "xml",
                datafields: [
                { name: 'Title', type: 'string' },
                { name: 'First Name', type: 'string' },
                { name: 'Middle Name', type: 'string' },
                { name: 'Last Name', type: 'string' }
                ],
                async: false,
                record: 'Table',
                url: 'Default.aspx/GetCustomers',
                data: '{ data1:' + tt + '}',//Error
                success: alert(data.d)
            };
            var dataAdapter = new $.jqx.dataAdapter(source,
                {  contentType: 'application/json; charset=utf-8'}
            );
            $("#jqxgrid").jqxGrid({
                source: dataAdapter,
                theme: 'classic',
                columns: [
                    { text: 'Title', dataField: 'Title', width: 50 },
                    { text: 'First Name', dataField: 'First Name', width: 250 },
                    { text: 'Middle Name', dataField: 'Middle Name', width: 250 },
                    { text: 'Last Name', dataField: 'Last Name', width: 250 }
                ]
            });
        };
    </script>

protected static DataSet GetData(string data)
        {
            DataSet ds = new DataSet();
            DataTable dt = new DataTable();
            if (dt == null)
            {
                dt.Columns.Add("Title", typeof(string));
                dt.Columns.Add("First Name", typeof(string));
                dt.Columns.Add("Middle Name", typeof(string));
                dt.Columns.Add("Last Name", typeof(string));
            }
            else
            {
                dt = HttpContext.Current.Session["MyTable"] as DataTable;
            }

            string[] split = data.Split('|');

            DataRow dr = dt.NewRow();
            dr["Title"] = split[0];
            dr["First Name"] = split[1];
            dr["Middle Name"] = split[2];
            dr["Last Name"] = split[3];
            dt.Rows.Add(dr);

            HttpContext.Current.Session["MyTable"] = dt;

            ds.Tables.Add(dt);
            return ds;
        }

        [WebMethod]
        [ScriptMethod(UseHttpGet = true, ResponseFormat = ResponseFormat.Xml)]
        public static string GetCustomers(string data1)
        {
            // Populate the DataSet.
            DataSet data = GetData(data1);
            // return the Customers table as XML.
            StringWriter writer = new StringWriter();
            data.Tables[0].WriteXml(writer, XmlWriteMode.WriteSchema, false);
            return writer.ToString();
        }