Create Dynamic Menu and Submenu in Asp.net

Create two Method one for Menu and another one for Sub-Menu both Method return string data. Menu data put in your menu control. like that see below...
Code:

string Menu(List<menuitems> menuItems)
{
    string strMenu="";
    foreach(MenuItems item in menuItems)
    {
        //It's demo menu tag, replace using your menu tag
        strMenu+="<a href=""+item.Url+"">"item.Name
        strMenu+=SubMenu(item.SubMenuItems);
        strMenu+="</a>";
    }
    return strMenu;
}

string SubMenu(List<submenuitems> subMenuItems)
{
    string strSubMenu="";
    foreach(SubMenuItems item in subMenuItems)
    {
        //It's demo sub-menu tag, replace using your sub-menu tag
        strSubMenu+="<a href=""+item.Url+"">"item.Name
        strSubMenu+="</a>";
    }
    return strSubMenu;
}

//Then in your page load event write below code...
protected void Page_Load(object sender, EventArgs e)
{
    //let divMenu your menu control or container.
    List<MenuItems> menuItems=new List<MenuItems>(); //Select menu list here...
    divMenu.innerHtml=Menu(menuItems);
}

Try this maybe it's work for you...