No response BIND Data to gridview using jquery

Question

Pls help why no response BIND Data to gridview using jquery as below:-

 

1) WebForm6.aspx

<script type="text/javascript"> src="http://code.jquery.com/jquery-1.11.1.min.js" </script>
<script type="text/javascript">
$(document).ready(function () {
BindGridView();
});
function BindGridView() {
$.ajax({
type: "POST",
url: "WebForm6.aspx/GetData",
contentType: "application/json;charset=utf-8",
data: {},
dataType: "json",
success: function (data) {
$("#grdDemo").empty();
if (data.d.length > 0) {
$("#grdDemo").append("<tr><th>Username</th><th>Firstname</th></tr>"); //<th>Lastname</th><th>EmailID</th>
for (var i = 0; i < data.d.length; i++) {
$("#grdDemo").append("<tr><td>" +
data.d[i].Firstname + "</td> <td>" +
data.d[i].Lastname + "</td></tr>");
}
}
},
error: function (result) {
alert("Error login");
}
});
}
</script>

2) WebForm6.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
BindDummyItem();
}
public void BindDummyItem()
{
DataTable dtGetData = new DataTable();
dtGetData.Columns.Add("Username");
dtGetData.Columns.Add("Firstname");
//dtGetData.Columns.Add("Lastname");
//dtGetData.Columns.Add("EmailID");
dtGetData.Rows.Add();
grdDemo.DataSource = dtGetData;
grdDemo.DataBind();
}
[WebMethod]
public static DetailsClass[] GetData() //GetData function
{
List<DetailsClass> Detail = new List<DetailsClass>();
string SelectString = "SELECT Username,Firstname FROM TABLE";
OracleConnection cn = new OracleConnection();
cn.ConnectionString = "Data Source=(DESCRIPTION ="
+ "(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=xxx.xxx.xxx.xxx)(PORT=xxx)))"
+ "(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=xxxxxx)));"
+ "User Id=xxx;Password=xxxxxx;";
OracleCommand cmd = new OracleCommand(SelectString, cn);
cn.Open();
OracleDataAdapter da = new OracleDataAdapter(cmd);
DataTable dtGetData = new DataTable();
da.Fill(dtGetData);
foreach(DataRow dtRow in dtGetData.Rows)
{
DetailsClass DataObj = new DetailsClass();
DataObj.Username = dtRow["Username"].ToString();
DataObj.Firstname = dtRow["Firstname"].ToString();
Detail.Add(DataObj);
}
return Detail.ToArray();
}
public class DetailsClass //Class for binding data
{
public string Username { get; set; }
public string Firstname { get; set; }
}