Problem when fetching data from database to autocomplete textbox

Search : <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

      <asp:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server"
                  ServiceMethod="AutoCompleteAjaxRequest"
                  ServicePath="AutoComplete.asmx"
                  MinimumPrefixLength="2"
                  CompletionInterval="100"
                  EnableCaching="false"
                  CompletionSetCount="10"
                  TargetControlID="TextBox1"
                  FirstRowSelected="false">
      </asp:AutoCompleteExtender>

In above code you can see that I have specified the TargetControlID="TextBox1" . This tag will used for specifying that in which control auto suggest will appear.

Now we will see hw to receive data from data base. For this in our AutoCompleteExtender tag we have two properties ServiceMethod and ServicePath . In this we will define web service name and method . For this add a webservice file in your project (.asmx). So here is the code of you webservice.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Data;
using System.Data.OleDb;

namespace ProjectDemo_Asp.et
{
    /// <summary>
    /// Summary description for AutoComplete
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
    [System.Web.Script.Services.ScriptService]
    public class AutoComplete : System.Web.Services.WebService
    {

        [WebMethod]
        public string[] AutoCompleteAjaxRequest(string prefixText, int count)
        {
            List<string> ajaxDataCollection = new List<string>();
            DataTable _objdt = new DataTable();
            _objdt = GetDataFromDataBase(prefixText);
                if(_objdt.Rows.Count>0)
                {
                    for (int i = 0; i < _objdt.Rows.Count; i++)
                    {
                        ajaxDataCollection.Add(_objdt.Rows[i]["LanguageName"].ToString());
                    }
                }
            return ajaxDataCollection.ToArray();
        }
        /// <summary>
        /// Function for retriving data from database
        /// </summary>
        /// <returns></returns>
        public DataTable GetDataFromDataBase(string prefixText)
        {
            string connectionstring = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\\bookstore.mdb;Persist Security Info=False;";
            DataTable _objdt = new DataTable();
            string querystring = "select * from ProLanguage where LanguageName like '%" + prefixText + "%';";
            OleDbConnection _objcon = new OleDbConnection(connectionstring);
            OleDbDataAdapter _objda = new OleDbDataAdapter(querystring, _objcon);
            _objcon.Open();
            _objda.Fill(_objdt);
            return _objdt;
        }
    }
}