AutoCompleteExtender Ajaxtoolkit Not Working

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C#

ASP.NET

Ajax

auto-complete

Dear Reader,

Following is my web service:

[WebService(Namespace = "http://tempuri.org/")]
   [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]

   [System.Web.Script.Services.ScriptService()]
   [System.ComponentModel.ToolboxItem(false)]

   public class WebService1 : System.Web.Services.WebService
   {

       [WebMethod]
       public string[] GetCities(string prefixText)
       {
           SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:Database.mdf;Integrated Security=True;MultipleActiveResultSets=True;Connect Timeout=30;Application Name=EntityFramework");
           con.Open();
           string strQuery = "select Source from Reservation where Source like '" + prefixText + "%'";
           DataSet ds = new DataSet();
           SqlDataAdapter da = new SqlDataAdapter(strQuery, con);
           da.Fill(ds);
           con.Close();
           List<string> cityList = new List<string>();
           for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
           {
               cityList.Add(ds.Tables[0].Rows[i][0].ToString());
           }
           con.Close();
           return cityList.ToArray();
       }
   }

The above service is working fine. I have tested in browser. It displays the expected output. Following is my code in aspx file:

<%@ Register TagPrefix="ac" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods = "true" ></asp:ScriptManager>
  <asp:TextBox ID="txtCity" runat="server" AutoCompleteType="Disabled"></asp:TextBox>
    <ac:AutoCompleteExtender ID="AutoCompleteExtender1"
       BehaviorID="AutoCompleteCities" TargetControlID="txtCity"
       ServiceMethod="GetCities" ServicePath="WebService1.asmx" MinimumPrefixLength="1"
        CompletionSetCount="10" CompletionInterval="100" EnableCaching="false"
       runat="server" FirstRowSelected = "false" >
 </ac:AutoCompleteExtender>

I don't know why the above code is not working. There is no such error but the text box doesn't show the autocomplete data generated from web method.

Please help me to solve this problem I will be very thankful to you.

Regards,