SharePoint 2010 top level navigation code. Built with a nested ASP:Repeater control. Easier to style with Bootstrap or Flexbox than the ASP:Menu control. Includes highlighting of the current section.

SP2010 ASP:Repeater-based navigation with current item selection.aspx

<!-- top navigation publishing data source -->
<PublishingNavigation:PortalSiteMapDataSource
    id="topSiteMap"
    runat="server"
    EnableViewState="false"
    SiteMapProvider="GlobalNavigation"
    StartFromCurrentNode="false"
    StartingNodeOffset="0"
    ShowStartingNode="true"
    TrimNonCurrentTypes="Heading"/>
<!--
    Repeater outputs a single level list of top-navigation.
    Sets class="selected" on the current page / site.
    This is much easier to adapt to use with Bootstrap or flexbox than the asp:menu control.
    Based on a post by Bhavin Prajapati - http://sharepoint2010customnavigation.blogspot.co.uk/2011/05/create-custom-navigation-for.html
-->
<asp:Repeater runat="server" ID="MenuRepeater" DataSourceID="topSiteMap">
    <HeaderTemplate>
        <ul>
    </HeaderTemplate>
    <SeparatorTemplate></SeparatorTemplate>
    <ItemTemplate>
        <li>
            <a  href="<%# Eval("Url")%>"
                class="<%# (Request.RawUrl.ToString().ToLower().Split('/')[1] == Eval("Url").ToString().ToLower().Split('/')[1]) ? "selected" : "" %>">
                <%# Eval("Title")%>
            </a>
        </li>
        <asp:Repeater runat="server" ID="ChildMenuRepeater" DataSource='<%# ((SiteMapNode)Container.DataItem).ChildNodes %>'>
            <HeaderTemplate></HeaderTemplate>
            <ItemTemplate>
                <li>
                    <a  href="<%# Eval("Url")%>" 
                        class="<%# (Request.RawUrl.ToString().ToLower().Split('/')[1] == Eval("Url").ToString().ToLower().Split('/')[1]) ? "selected" : "" %>">
                        <%# Eval("Title")%>
                    </a>
                </li>
            </ItemTemplate>
            <FooterTemplate></FooterTemplate>
        </asp:Repeater>
    </ItemTemplate>
   <FooterTemplate>
       </ul>
   </FooterTemplate>
</asp:Repeater>