Dynamic Menu And Sub Menu From Database

Css

<div>
<ul id="nav" runat="server"></ul> 
</div>

Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.OleDb;
using System.Data;
using System.Configuration;

public partial class home : System.Web.UI.Page
{
    Code objcode = new Code();

    protected void Page_Load(object sender, EventArgs e)
    {
        menu();
    }

    public void menu()
    {
        string content = string.Empty;
        OleDbConnection con = new OleDbConnection(ConfigurationManager.ConnectionStrings["datacon"].ConnectionString);
        con.Open();
        OleDbCommand cmd = new OleDbCommand("select * from menu", con);
        OleDbDataAdapter ad = new OleDbDataAdapter(cmd);
        DataTable dt = new DataTable();
        ad.Fill(dt);
        if (dt.Rows.Count > 0)
        {
            foreach (DataRow dr in dt.Rows)
            {
                string st="#";
                content += "<li><a href='" + st + "'>" + dr["menu_name"] + "</a>" + submenu(dr["menu_name"].ToString()) + "</li>";               
            }
            nav.InnerHtml = content;
        }
    }

    public string submenu(string str)
    {
        string content = string.Empty;
        content += "<ul>";
        if (str.Trim() == "About Us")
        {
            content += bindmainmenu();
        }

        if (str.Trim() == "Contact Us")
        {
            content += bindmainmenu2();
        } 
        content += "</ul>";
        return content;
    }


    public string bindmainmenu()
    {
        string content = string.Empty;
        OleDbConnection con = new OleDbConnection(ConfigurationManager.ConnectionStrings["datacon"].ConnectionString);
        con.Open();
        OleDbCommand cmd = new OleDbCommand("select * from sub_menu", con);
        OleDbDataAdapter ad = new OleDbDataAdapter(cmd);
        DataTable dt = new DataTable();
        ad.Fill(dt);
        if (dt.Rows.Count > 0)
        {
            foreach (DataRow dr in dt.Rows)
            {
                content += "<li><a href='" + dr["menu_url"] + "?pid=" + dr["id"] + "'" + ">" + dr["menu_name"] + "</a></li>";
            }
        }        
        return content;
    }

    public string bindmainmenu2()
    {
        string content = string.Empty;
        OleDbConnection con = new OleDbConnection(ConfigurationManager.ConnectionStrings["datacon"].ConnectionString);
        con.Open();
        OleDbCommand cmd = new OleDbCommand("select * from sub_menu2", con);
        OleDbDataAdapter ad = new OleDbDataAdapter(cmd);
        DataTable dt = new DataTable();
        ad.Fill(dt);
        if (dt.Rows.Count > 0)
        {
            foreach (DataRow dr in dt.Rows)
            {
                content += "<li><a href='" + dr["menu_url"] + "?pid=" + dr["id"] + "'" + ">" + dr["menu_name"] + "</a></li>";
            }
        }
        return content;
    }
}