How to solve web service not working in AutoCompleteExtender?

Make sure added [System.Web.Script.Services.ScriptService] into class level of web service

using System;

using System.Collections.Specialized;

using System.Web.Services;

namespace testauto

{

    [WebService(Namespace = "http://tempuri.org/")]

    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]

    [System.ComponentModel.ToolboxItem(false)]

    [System.Web.Script.Services.ScriptService]

    public class test : System.Web.Services.WebService

    {

        [System.Web.Services.WebMethod]

        [System.Web.Script.Services.ScriptMethod]

        public string[] GetCompletionList(string prefixText, int count)

        {

            StringCollection names = new StringCollection();

            names.Add("a");

            names.Add("ab");

            names.Add("abc");

            names.Add("b");

            names.Add("bb");

            String[] namesarray = new String[names.Count];

            names.CopyTo(namesarray, 0);

            return namesarray;

        }

    }

}

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

        <asp:AutoCompleteExtender ID="TextBox1_AutoCompleteExtender" runat="server" TargetControlID="TextBox1" ServiceMethod="GetCompletionList" ServicePath="~/test.asmx" MinimumPrefixLength="2" CompletionInterval="1000" EnableCaching="true" CompletionSetCount="20">

        </asp:AutoCompleteExtender>