关于SlideShowExtender的一个小问题

Default.aspx<form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
         <asp:Image ID="Image1" runat="server" Height="175px" Width="300px"  ImageUrl="~/Images/Chrysanthemum.jpg" /><br />
        <asp:Label ID="Label_Title" runat="server"></asp:Label><br />
         <asp:Label ID="Label_Description" runat="server"></asp:Label><br />
         <asp:Button ID="Button_Preview" runat="server" Text="上一个" />
         <asp:Button ID="Button_Stop" runat="server" Text="停止" />
         <asp:Button ID="Button_Next" runat="server" Text="下一个" /><br />
         <cc1:SlideShowExtender ID="SlideShowExtender1" runat="server" AutoPlay="True" 
            Loop="True" SlideShowServiceMethod="GetSlides"                 SlideShowServicePath="~/SlideShowWebService.asmx"
            TargetControlID="Image1" ImageDescriptionLabelID="Label_Description" ImageTitleLabelID="Label_Title" NextButtonID="Button_Next" PlayButtonID="Button_Stop" PlayButtonText="播放" PreviousButtonID="Button_Preview" StopButtonText="停止" >
        </cc1:SlideShowExtender>
    </form>
SlideShowWebServicepublic class SlideShowWebService : System.Web.Services.WebService
    {
        [WebMethod]
        [System.Web.Script.Services.ScriptMethod]
        public static AjaxControlToolkit.Slide[] GetSlides()
        {
            string serverPath = System.Web.HttpContext.Current.Server.MapPath(".");
            string path = Path.Combine(serverPath, "Images");
            DirectoryInfo dir = new DirectoryInfo(path);
            int i = 0;
            int j = dir.GetFiles().Length;
            AjaxControlToolkit.Slide[] act = new AjaxControlToolkit.Slide[j];
            foreach (FileInfo fi in dir.GetFiles())
            {
                act[i] = new AjaxControlToolkit.Slide(fi.FullName, fi.Name, fi.Name.Substring(0, fi.Name.IndexOf(".")));
                i = i + 1;
            }
            return act;
        }
    }错误 1.Microsoft JScript 运行时错误: Sys.Net.WebServiceFailedException: 服务器方法“GetSlides”失败，并发生以下错误: <html>
    <head>
        <title>未知 Web 方法 GetSlides。<br>参数名: methodName</title>
 。。
2.若把WebService那段放到Default.aspx.cs结果是没反应，act中是有数据的