If CurrentPage add active class

Questions
1

Hi Guys
I'm trying to make my first Razor navigation.

My problem right now is I really don't know how to add an class to my active node.

Can anyone help me with this - and maybe try to make me understand?

@inherits Umbraco.Web.Mvc.UmbracoTemplatePage

@{


if (Model.Content.AncestorOrSelf(1).Children.Count() > 0) 
{
    <ul id="navigationBar" class="nav navbar-nav">
        @foreach (var mainNodes in Model.Content.AncestorOrSelf(1).Children.Where("TemplateId != 0 && Visible"))
        {

            if (mainNodes.Children.Where("TemplateId != 0 && Visible").Count() > 0)
            {
                <li class="@(mainNodes.IsAncestorOrSelf(CurrentPage) ? "active" : null)">
				    <a href="#" class="dropdown-toggle" data-toggle="dropdown">@mainNodes.Name<b class="caret"></b></a>

                    <ul class="dropdown-menu">

                        @foreach(var subNodes in mainNodes.Children.Where("TemplateId !=0 && Visible"))
                        
                        {
                            <li><a href="@subNodes.Url">@subNodes.Name</a></li>
                        }

                    </ul>

			    </li>
                
            }else{
                <li>
				    <a href="@mainNodes.Url">@mainNodes.Name</a>
                    @if(CurrentPage.AncestorOrSelf.Id == mainNodes.Id ){
                        <span>juhu</span>
                    }
			    </li>
            }
        }
    </ul>
 }  



}

This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/48200-if-currentpage-add-active-class