AutoCompleteExtraExtender无反应

前台：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="testpy.aspx.cs" Inherits="testpy" %><%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
    Namespace="System.Web.UI" TagPrefix="asp" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc2" %>
<%@ Register Assembly="AutoCompleteExtra" Namespace="AutoCompleteExtra" TagPrefix="cc1" %> 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
   
        <cc2:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server" ScriptMode="Release">
        </cc2:ToolkitScriptManager>
     
            <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:TextBox ID="txtName" runat="server" Width="200" ></asp:TextBox>
                <cc1:AutoCompleteExtraExtender ID="AutoCompleteExtraExtender1" runat="server" ServicePath="sql_test.asmx"  ServiceMethod="GetCompleteList"  CompletionSetCount="10"
MinimumPrefixLength="1" TargetControlID="txtName" CompletionInterval="300" >
                </cc1:AutoCompleteExtraExtender>
            </ContentTemplate>
        </asp:UpdatePanel>
     </form>
</body>
</html>后台：
using System;
using System.Collections;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Collections.Generic;
 
[WebService(Namespace = "http://tempuri.org/")] 
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] 
[System.Web.Script.Services.ScriptService]
public class sql_test : System.Web.Services.WebService {     public sql_test () {         //如果使用设计的组件，请取消注释以下行 
        //InitializeComponent(); 
    }     [WebMethod] 
    public string[] GetCompleteList(string prefixText, int count) 
    { 
           string sqlstr="Server=(local);User id=sa;Pwd=;Database=zlsf";//数据库连接 
        SqlConnection sqlconn = new SqlConnection(sqlstr);
        string mysql = "select lczd from lczd where dbo.f_GetPy(lczd) like '" + prefixText + "%' order by lczd";
        SqlDataAdapter da = new SqlDataAdapter(mysql, sqlconn);
        DataSet ds = new DataSet();
        da.Fill(ds, "studentname");
        string[] returnvalue = new string[ds.Tables["studentname"].Rows.Count];
        for (int i = 1; i <= ds.Tables["studentname"].Rows.Count; i++)
        {
            returnvalue[i - 1] = ds.Tables["studentname"].Rows[i - 1][0].ToString();
        }
        return (returnvalue);    } 
    
}