vs2008 menu控件子菜单显示不出来

Question

前台代码：
Font-Names="宋体" Font-Size="9pt" ForeColor="White" Orientation="Horizontal"
StaticSubMenuIndent="10px" OnMenuItemClick="menuNav_MenuItemClick"
DynamicPopOutImageTextFormatString="" Height="22px" Width="658px">







/asp:MenuItem

/asp:MenuItem
/asp:MenuItem
/asp:MenuItem
/asp:MenuItem

/asp:MenuItem
/asp:MenuItem
/asp:MenuItem

/asp:MenuItem
/asp:MenuItem
/asp:MenuItem

/asp:MenuItem
/asp:MenuItem
/asp:MenuItem

/asp:MenuItem
/asp:MenuItem
/asp:MenuItem

/asp:MenuItem
/asp:MenuItem
/asp:MenuItem
/asp:MenuItem
/asp:MenuItem


/asp:Menu

后台代码：
protected void Page_Load(object sender, EventArgs e)
{
if (Session["role"] == "Reader")
{
menuNav.Items[1].Enabled = false;
menuNav.Items[2].Enabled = false;
menuNav.Items[3].Enabled = false;
menuNav.Items[5].Enabled = false;
}
else
{
if (Session["Name"] != null)
{
labAdmin.Text = Session["Name"].ToString();
adminmanage.Name = Session["Name"].ToString();
}
DataSet adminds = adminmanage.GetAllAdminByName(adminmanage, "tb_admin");
string strAdminID = adminds.Tables[0].Rows[0][0].ToString();
purviewmanage.ID = strAdminID;
DataSet pviewds = purviewmanage.FindPurviewByID(purviewmanage, "tb_purview");
bool sysset = Convert.ToBoolean(pviewds.Tables[0].Rows[0][1].ToString());
bool readset = Convert.ToBoolean(pviewds.Tables[0].Rows[0][2].ToString());
bool bookset = Convert.ToBoolean(pviewds.Tables[0].Rows[0][3].ToString());
bool borrowback = Convert.ToBoolean(pviewds.Tables[0].Rows[0][4].ToString());
bool sysquery = Convert.ToBoolean(pviewds.Tables[0].Rows[0][5].ToString());

        if (sysset == true)
        {
            menuNav.Items[1].Enabled = true;
        }
        else
        {
            menuNav.Items[1].Enabled = false;
        }

        if (readset == true)
        {
            menuNav.Items[2].Enabled = true;
        }
        else
        {
            menuNav.Items[2].Enabled = false;
        }

        if (bookset == true)
        {
            menuNav.Items[3].Enabled = true;
        }
        else
        {
            menuNav.Items[3].Enabled = false;
        }

        if (borrowback == true)
        {
            menuNav.Items[4].Enabled = true;
        }
        else
        {
            menuNav.Items[4].Enabled = false;
        }

        if (sysquery == true)
        {
            menuNav.Items[5].Enabled = true;
        }
        else
        {
            menuNav.Items[5].Enabled = false;
        }
    }
}
protected void menuNav_MenuItemClick(object sender, MenuEventArgs e)
{
    if (menuNav.SelectedValue == "退出系统")
    {
        Response.Write("<script>window.close();</script>");
    }
}