Hey baits,

Please refer below sample.

HTML

<div>
    <div>
        <div class="navbar navbar-default">
            <div class="container-fluid">
                <div class="navbar-header">
                    <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1"
                        aria-expanded="false">
                        <span class="sr-only">Toggle navigation</span> <span class="icon-bar"></span><span
                            class="icon-bar"></span><span class="icon-bar"></span>
                    </button>
                    <a class="navbar-brand" href="#">ASPSnippets</a>
                </div>
                <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
                    <asp:Menu ID="Menu1" runat="server" Orientation="Horizontal" RenderingMode="List"
                        IncludeStyleBlock="false" StaticMenuStyle-CssClass="nav navbar-nav" DynamicMenuStyle-CssClass="dropdown-menu">
                    </asp:Menu>
                </div>
            </div>
        </div>
        <hr />
    </div>
</div>
<link rel="stylesheet" href='http://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.0.3/css/bootstrap.min.css'
    media="screen" />
<script type="text/javascript" src='http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.8.3.min.js'></script>
<script type="text/javascript" src='http://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.0.3/js/bootstrap.min.js'></script>
<style type="text/css">
    .dropdown-submenu
    {
        position: relative;
    }
    .dropdown-submenu > .dropdown-menu
    {
        top: 0;
        left: 100%;
        margin-top: -6px;
        margin-left: -1px;
        -webkit-border-radius: 0 6px 6px 6px;
        -moz-border-radius: 0 6px 6px 6px;
        border-radius: 0 6px 6px 6px;
    }
    .dropdown-submenu > a:after
    {
        display: block;
        content: " ";
        float: right;
        width: 0;
        height: 0;
        border-color: transparent;
        border-style: solid;
        border-width: 5px 0 5px 5px;
        border-left-color: #cccccc;
        margin-top: 5px;
        margin-right: -10px;
    }
    .dropdown-submenu:hover > a:after
    {
        border-left-color: #555;
    }
    .dropdown-submenu.pull-left
    {
        float: none;
    }
    .dropdown-submenu.pull-left > .dropdown-menu
    {
        left: -100%;
        margin-left: 10px;
        -webkit-border-radius: 6px 0 6px 6px;
        -moz-border-radius: 6px 0 6px 6px;
        border-radius: 6px 0 6px 6px;
    }
</style>
<script type="text/javascript">
    //Disable the default MouseOver functionality of ASP.Net Menu control.
    //        Sys.WebForms.Menu._elementObjectMapper.getMappedObject = function () {
    //            return false;
    //        };
    $(function () {
        $(".navbar-nav li, .navbar-nav a, .navbar-nav ul").removeAttr('style');
        $(".dropdown-menu").closest("li").removeClass().addClass("dropdown-toggle");
        $(".dropdown-toggle").find("a[href='javascript:;']").attr("data-toggle", "dropdown");
        $(".dropdown-toggle").find("a[href='javascript:;'].level1").append("<span class='caret'></span>");
        $(".dropdown-toggle").find("a[href='javascript:;']:not(.level1)").closest('li').addClass('dropdown-submenu');
        $("a.selected").closest("li").addClass("active");
        $("a.selected").closest(".dropdown-toggle").addClass("active");
        $('ul.dropdown-menu [data-toggle=dropdown]').on('click', function (event) {
            event.preventDefault();
            event.stopPropagation();
            $(this).parent().siblings().removeClass('open');
            $(this).parent().toggleClass('open');
        });
    });
</script>

Namespaces

C#

using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.IO;

VB.Net

Imports System.Data
Imports System.IO
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = this.GetData();
        PopulateMenu(dt);
    }
}

private DataTable GetData()
{
    string query = "SELECT [MenuId], [ParentMenuId], [Title], [Description], [Url] FROM [TestMenus]";
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        DataTable dt = new DataTable();
        using (SqlCommand cmd = new SqlCommand(query))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.CommandType = CommandType.Text;
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                sda.Fill(dt);
            }
        }
        return dt;
    }
}

private void PopulateMenu(DataTable dt)
{
    string currentPage = Path.GetFileName(Request.Url.AbsolutePath);
    DataView view = new DataView(dt);
    view.RowFilter = "ParentMenuId=0";
    foreach (DataRowView row in view)
    {
        MenuItem menuItem = new MenuItem
        {
            Value = row["MenuId"].ToString(),
            Text = row["Title"].ToString(),
            NavigateUrl = row["Url"].ToString(),
            Selected = row["Url"].ToString().EndsWith(currentPage, StringComparison.CurrentCultureIgnoreCase)
        };
        Menu1.Items.Add(menuItem);
        AddChildItems(dt, menuItem);
    }
}

private void AddChildItems(DataTable table, MenuItem menuItem)
{
    DataView viewItem = new DataView(table);
    viewItem.RowFilter = "ParentMenuId=" + menuItem.Value;
    foreach (DataRowView childView in viewItem)
    {
        MenuItem childmenuItem = new MenuItem
        {
            Value = childView["MenuId"].ToString(),
            Text = childView["Title"].ToString(),
            NavigateUrl = childView["Url"].ToString(),
        };
        menuItem.ChildItems.Add(childmenuItem);
        AddChildItems(table, childmenuItem);
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As DataTable = Me.GetData()
        PopulateMenu(dt)
    End If
End Sub

Private Function GetData() As DataTable
    Dim query As String = "SELECT [MenuId], [ParentMenuId], [Title], [Description], [Url] FROM [TestMenus]"
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Dim dt As DataTable = New DataTable()
        Using cmd As SqlCommand = New SqlCommand(query)
            Using sda As SqlDataAdapter = New SqlDataAdapter()
                cmd.CommandType = CommandType.Text
                cmd.Connection = con
                sda.SelectCommand = cmd
                sda.Fill(dt)
            End Using
        End Using
        Return dt
    End Using
End Function

Private Sub PopulateMenu(ByVal dt As DataTable)
    Dim currentPage As String = Path.GetFileName(Request.Url.AbsolutePath)
    Dim view As DataView = New DataView(dt)
    view.RowFilter = "ParentMenuId=0"
    For Each row As DataRowView In view
        Dim menuItem As MenuItem = New MenuItem With {
            .Value = row("MenuId").ToString(),
            .Text = row("Title").ToString(),
            .NavigateUrl = row("Url").ToString(),
            .Selected = row("Url").ToString().EndsWith(currentPage, StringComparison.CurrentCultureIgnoreCase)
        }
        Menu1.Items.Add(menuItem)
        AddChildItems(dt, menuItem)
    Next
End Sub

Private Sub AddChildItems(ByVal table As DataTable, ByVal menuItem As MenuItem)
    Dim viewItem As DataView = New DataView(table)
    viewItem.RowFilter = "ParentMenuId=" & menuItem.Value
    For Each childView As DataRowView In viewItem
        Dim childmenuItem As MenuItem = New MenuItem With {
            .Value = childView("MenuId").ToString(),
            .Text = childView("Title").ToString(),
            .NavigateUrl = childView("Url").ToString()
        }
        menuItem.ChildItems.Add(childmenuItem)
        AddChildItems(table, childmenuItem)
    Next
End Sub

Screenshot