How to navigate to a page using html helper class in navigation drop down menu

Question

I'm using navigation drop down menu. This is my coding:

 @if (@Html.Controller() == "Function" && @Html.Action() == "Dashboard")
        {
            <li class="active">
                @Html.ActionLink("Function", "Index", "Function")
            </li>
        }

  else
    {
        <li>@Html.ActionLink("Client", "Index", "Client")</li>
    }

  @if (@Html.Controller() == "Report")
        {

        <li class="dropdown">
         <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="menu">
                Report
         <b class="caret"></b>
            </a>
         <ul class="dropdown-menu">
         <li><a href="#">a</a></li>
         <li><a href="#">b </a></li>

         </ul>
         </li>

    }
    else
    {
        <li>@Html.ActionLink("Report", "Index", "Report")</li>
    } 

I know how I can navigate to Functions page. But I am not sure how to navigate to drop down a using @Html.ActionLink which is present in Report drop down