VS2008中AutoCompleteExtender控件问题

我用AutoCompleteExtender控件做了一个测试,但是我在TEXTBOX中输入内容,在下拉列表中不能显示出来相关的内容.

下面我把两代码程序贴出来,大家指点一下.

页面

<asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <br />
     <asp:TextBox ID="MyAuto" runat="server" Width="191px"></asp:TextBox><br />
            <br />
            <cc1:AutoCompleteExtender ID="ace" runat="server" CompletionInterval="100" MinimumPrefixLength="1"
                ServiceMethod="GetCompultionList" ServicePath="WebService.asmx" TargetControlID="MyAuto">
            </cc1:AutoCompleteExtender>

 

WebService.asmx代码中

 

 [WebMethod]
    public string[] GetCompultionList(string text,int count)
    {
        Random random = new Random();
        List<string> items = new List<string>(count);
        for (int i = 0; i < count; i++)
        {
            char c1=(char)random.Next(65,90);
            char c2 = (char)random.Next(97,122);
            char c3 = (char)random.Next(48, 57);
            char c4 = (char)random.Next(33, 43);
            items.Add(text + c1 + c2 + c3 + c4);

        }
        return items.ToArray();
    }