Code
<ext:MenuPanel ID="MenuPanel1" runat="server" Height="300" Title="Menu" Width="185">
    <Menu>
        <Items>
            <ext:MenuItem ID="MenuItem1" runat="server" Text="Item1">
                <Menu>
                    <ext:Menu ID="Menu2" runat="server">
                        <Items>
                            <ext:MenuItem ID="MenuItem2" runat="server" Text="SubItem1">
                            </ext:MenuItem>
                            <ext:MenuItem ID="MenuItem3" runat="server" Text="SubItem2">
                            </ext:MenuItem>
                        </Items>
                    </ext:Menu>
                </Menu>
            </ext:MenuItem>
            <ext:MenuItem ID="MenuItem4" runat="server" Text="Item2">
            </ext:MenuItem>
            <ext:MenuItem ID="MenuItem5" runat="server" Text="Item3">
            </ext:MenuItem>
            <ext:MenuItem ID="MenuItem6" runat="server" Text="Item4">
            </ext:MenuItem>
        </Items>
    </Menu>
</ext:MenuPanel>

<ext:MenuPanel runat="server" Height="300" Title="帐套管理" Width="185">
    <Menu runat="server">
        <Items>
            <ext:MenuItem runat="server" Text="新增帐套" Icon="Add">
                <Listeners>
                    <Click Handler="JavaScript:window.location.href='#';" />
                </Listeners>
            </ext:MenuItem>
            <ext:MenuItem runat="server" Text="维护帐套" Icon="Cmy"/>
            <ext:MenuItem runat="server" Text="帐套管理" Icon="Database">
                <Menu>
                    <ext:Menu runat="server">
                        <Items>
                            <ext:MenuItem  runat="server" Text="备份帐套" Icon="DatabaseSave">
                                <Listeners>
                                    <Click Handler="JavaScript:window.open('#');" />
                                </Listeners>
                            </ext:MenuItem>
                            <ext:MenuItem runat="server" Text="恢复帐套" Icon="DatabaseGo">
                                <Listeners>
                                    <Click Handler="JavaScript:window.open('#');" />
                                </Listeners>
                            </ext:MenuItem>
                        </Items>
                    </ext:Menu>
                </Menu>
            </ext:MenuItem>
        </Items>
        <Listeners>
            <ItemClick Fn="onItemClick" />
        </Listeners>
    </Menu>
</ext:MenuPanel>
<script type="text/javascript">
    function onItemClick(menuItem) {
        Ext.Msg.alert("★操作提示★", "当前点击项内容：" + menuItem.text);
    }
 </script>

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        CreateMenuPanel();
    }
}

private void CreateMenuPanel()
{
    MenuPanel menuPanel = new MenuPanel();
    menuPanel.Title = "帐套管理";
    menuPanel.Width = new Unit(180);

Coolite.Ext.Web.MenuItem addAccount = new Coolite.Ext.Web.MenuItem("新增帐套");
    addAccount.Icon = Icon.Add;
    addAccount.Listeners.Click.Handler = "JavaScript:window.location.href='#';";
    
    Coolite.Ext.Web.MenuItem whAccount = new Coolite.Ext.Web.MenuItem("维护帐套");
    whAccount.Icon=Icon.Cmy;

Coolite.Ext.Web.MenuItem accountManage = new Coolite.Ext.Web.MenuItem("帐套管理");
    accountManage.Icon = Icon.Database;

Coolite.Ext.Web.Menu subMenu = new Coolite.Ext.Web.Menu();

Coolite.Ext.Web.MenuItem backMenuItem = new Coolite.Ext.Web.MenuItem("备份帐套");
    backMenuItem.Icon = Icon.DatabaseSave;
    backMenuItem.Listeners.Click.Handler = "JavaScript:window.open('#')";
    subMenu.Items.Add(backMenuItem);

Coolite.Ext.Web.MenuItem reMenuItem = new Coolite.Ext.Web.MenuItem("恢复帐套");
    reMenuItem.Icon = Icon.DatabaseGo;
    reMenuItem.Listeners.Click.Handler = "JavaScript:window.open('#')";
    subMenu.Items.Add(reMenuItem);

accountManage.Menu.Add(subMenu);

menuPanel.Menu.Items.Add(addAccount);
    menuPanel.Menu.Items.Add(whAccount);
    menuPanel.Menu.Items.Add(accountManage);
    menuPanel.Menu.Listeners.ItemClick.Fn = "onItemClick";

accountDiv.Controls.Add(menuPanel);
}