asp.net动态创建列表框

Question

我希望显示类似于Ebay用于类别选择的动态列表框

http://cgi5.ebay.com/ws/eBayISAPI.dll?NewListing&sid=&cpg=134&aid=6（您必须登录以查看类别的工作方式）

以下是屏幕截图：Ebay Screenshot http://www.aquariumbids.com/Images/ebayCat.JPG

任何解释此代码或代码示例的文档的链接都将不胜感激。

到目前为止，这是我的代码：

    protected void Page_Load(object sender, EventArgs e)
    {
        ListBox Temp = CreateListBox();
        UpdatePanel1.ContentTemplateContainer.Controls.Add(Temp);
        PlaceHolder1.Controls.Add(Temp);
    }

    /// <summary>
    /// 
    /// </summary>
    /// <returns></returns>
    protected ListBox CreateListBox()
    {
        ListBox lb = new ListBox();
        DataTable Categories = Globals.g_DatabaseHandler.GetRecords(StoredProcedures.GetMainCategories, new Dictionary<string, string>() { });

        foreach (DataRow row in Categories.Rows)
        {
            lb.Items.Add(new ListItem(row[1].ToString(), row[0].ToString()));
        }

        lb.AutoPostBack = true;
        lb.CssClass = "panel";
        lb.SelectedIndexChanged += new EventHandler(ListBox_SelectionChanged);

        return lb;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="CatId"></param>
    /// <returns></returns>
    protected ListBox CreateListBox(string CatId)
    {
        ListBox lb = new ListBox();
        Dictionary<string, string> Params = new Dictionary<string, string>();
        Params.Add("parentID", CatId);
        DataTable Categories = Globals.g_DatabaseHandler.GetRecords(StoredProcedures.GetChildCategories, Params);

        if (Categories.Rows.Count > 0)
        {
            foreach (DataRow row in Categories.Rows)
            {
                lb.Items.Add(new ListItem(row[1].ToString(), row[0].ToString()));
            }

            lb.AutoPostBack = true;
            lb.CssClass = "panel";
            lb.SelectedIndexChanged += new EventHandler(ListBox_SelectionChanged);
        }
        return lb;
    }

    protected void ListBox_SelectionChanged(object sender, EventArgs arg)
    {
        string ID = ((ListBox)sender).SelectedValue;

        ListBox Temp = CreateListBox(ID);
        UpdatePanel1.ContentTemplateContainer.Controls.Add(Temp);
        PlaceHolder1.Controls.Add(Temp);

    }

这是标记

<div id="wrapper">
            <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>                
            <asp:UpdatePanel ID="UpdatePanel1" runat="server">                    
                <ContentTemplate>
                    <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
                </ContentTemplate>
            </asp:UpdatePanel>
        </div>