Как использовать ajax auto complete extender в asp.net-что?

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Я пытаюсь искать данные из базы данных, но не могу получить результат.Пожалуйста, может ли любое тело помочь мне.
спасибо заранее

<asp:TextBox ID="txtlicense" runat="server"></asp:TextBox>
 <ajax:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server" TargetControlID="txtlicense"

 MinimumPrefixLength="1" EnableCaching="true" ServicePath="WebService.asmx"

  ServiceMethod="GetLicense" CompletionInterval="100"

  CompletionSetCount="10" >
  </ajax:AutoCompleteExtender>

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

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

    public WebService () {

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

    [WebMethod]
    public List<string> GetLicense(string prefixText)
 {
     SqlConnection con = new SqlConnection("Data Source=.;Integrated Security=True;Initial Catalog=LicenseManagementSystem");
        con.Open();
        SqlCommand cmd = new SqlCommand("select LicenseNumber from LicenseDetails where LicenseNumber like @license+'%'", con);
        cmd.Parameters.AddWithValue("@license", prefixText);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        da.Fill(dt);
        List<string> license = new List<string>();
        for (int i = 0; i < dt.Rows.Count; i++)

        {

            license.Add(dt.Rows[i][1].ToString());

        }

        return license;

    }

}

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