load empty data in form

load empty data in form

Hi,
I newer to work jquery,i write the program that the url equal a webservice url and web service connect to table of database and return 2 columns but when jquery use this url grid is empty,what i doing for solve this problem?

....

<link rel="stylesheet" type="text/css" media="screen" href="css/smoothness/jquery-ui-1.8.6.custom.css" />
<link rel="stylesheet" type="text/css" media="screen" href="css/ui.jqgrid.css" />
<link rel="stylesheet" type="text/css" media="screen" href="js/src/css/ui.jqgrid.css" />
<link rel="stylesheet" type="text/css" media="screen" href="js/src/css/jquery.searchFilter.css" />


<script src="js/jquery-1.4.2.min.js" type="text/javascript"></script>
<script src="js/src/grid.loader.js" type="text/javascript"></script>

<script src="js/js/i18n/grid.locale-en.js" type="text/javascript"></script>
<script src="js/jquery.jqGrid.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function() {
$("#list").jqGrid({
url: '/WebService.asmx/data',
datatype: 'xml',
mtype: 'GET',
colNames: ['Inv No', 'Date', 'Amount', 'Tax', 'Total', 'Notes'],
colModel: [
{ name: 'invid', index: 'invid', width: 55 },
{ name: 'invdate', index: 'invdate', width: 90 },
{ name: 'amount', index: 'amount', width: 80, align: 'right' },
{ name: 'tax', index: 'tax', width: 80, align: 'right' },
{ name: 'total', index: 'total', width: 80, align: 'right' },
{ name: 'note', index: 'note', width: 150, sortable: false }
],
pager: '#pager',
rowNum: 10,
rowList: [10, 20, 30],
sortname: 'invid',
sortorder: 'desc',
viewrecords: true,
caption: 'My first grid'
});
});
</script>
</head>
<body>
<table id="list"></table>
<div id="pager"></div>
</body>
</html>
webservice:

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Services;
using System.Data.SqlClient;
using System.Data;

/// <summary>
/// Summary description for WebService
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class WebService : System.Web.Services.WebService {

public WebService () {

//Uncomment the following line if using designed components
//InitializeComponent();
}

[WebMethod]
public DataTable data() {
//return "Hello World";
string strcon = "Data Source=as;Initial Catalog=MyProgramDB;Integrated Security=True";
SqlConnection sqlcon = new SqlConnection(strcon);
sqlcon.Open();
SqlCommand cmd = new SqlCommand("select * from invheader", sqlcon);
DataTable dt = new DataTable("invhead");
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
return dt;
sqlcon.Close();
}

}

please help me,
thanks