data load inside data list when page is scroll in c#

i will use this page like:

<%@ Page Title="" Language="C#" MasterPageFile="~/Admin/AdminMaster.master" AutoEventWireup="true"

CodeFile="Default6.aspx.cs" Inherits="Default6" %>

CellPadding="2" CellSpacing="20">

<%--

--%>

and code behind code like

============================================

protected void Page_Load(object sender, EventArgs e)

{

if (!IsPostBack)

{

dlImages.DataSource = GetCustomersData(1);

dlImages.DataBind();

}

public static DataSet GetCustomersData(int pageIndex)

{

string query = "[GetProductPageWise]";

SqlCommand cmd = new SqlCommand(query);

cmd.CommandType = CommandType.StoredProcedure;

cmd.Parameters.AddWithValue("@PageIndex", pageIndex);

cmd.Parameters.AddWithValue("@PageSize", 10);

cmd.Parameters.Add("@PageCount", SqlDbType.Int, 4).Direction = ParameterDirection.Output;

return GetData(cmd);

}

private static DataSet GetData(SqlCommand cmd)

{

string strConnString = ConfigurationManager.ConnectionStrings["FairDecoreConn"].ConnectionString;

using (SqlConnection con = new SqlConnection(strConnString))

{

using (SqlDataAdapter sda = new SqlDataAdapter())

{

cmd.Connection = con;

sda.SelectCommand = cmd;

using (DataSet ds = new DataSet())

{

sda.Fill(ds, "Tbl_Products");

DataTable dt = new DataTable("PageCount");

dt.Columns.Add("PageCount");

dt.Rows.Add();

dt.Rows[0][0] = cmd.Parameters["@PageCount"].Value;

ds.Tables.Add(dt);

return ds;

}

[WebMethod]

public static string GetCustomers(int pageIndex)

{

return GetCustomersData(pageIndex).GetXml();

}

when page scroll then it show message like:

undefined i'am not understand this means please any body solve this query