ajax AutoCompleteExtender 自动下拉text 不起作用也不出错

aspx文件-------------------------------------------------------------------------
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="DeliverGoods.aspx.cs" Inherits="produce_DeliverGoods" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>
<html xml:lang>
<head runat="server">
    <title>仓库发货</title>
</head>
<body class="frameborder">
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
   <div>
           
            <cc1:AutoCompleteExtender ID="AutoCompleteExtender2" TargetControlID="TextBox1" CompletionSetCount="12" 
          ServicePath="AutoComplete.asmx" ServiceMethod="GetCompletionList"   CompletionInterval="1000" EnableCaching="true" MinimumPrefixLength="2"  runat="server">
       </cc1:AutoCompleteExtender>         </div>
 <asp:TextBox ID="TextBox1" runat="server" Width="285px"  />
        
    </form>
</body>
</html>
AutoComplete.cs文件----------------------------------------------------------------------------------
using System;
using System.Web;
using System.Collections;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Collections.Generic;
/// <summary>
/// AutoComplete 的摘要说明
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService()]
     public class AutoComplete : System.Web.Services.WebService
    {         [WebMethod]
         public string[] GetCompletionList(string prefixText, int count)
         {
             string[] aa ={ "ttttttt", "ttttt333", "tttttcccc", "tttaasawsees", "tt77567567" };
             return aa;
        }
    }