      <li>
          <a href="#toc_what-is-a-controller">What is a Controller?</a>
        </li>
        <li>
          <a href="#toc_defining-a-controller">Defining a Controller</a>
        </li>
        <li>
          <a href="#toc_where-and-when-to-use-controllers">Where and When to use Controllers?</a>
        </li>
        <li>
          <a href="#toc_basic-controller-example">Basic Controller Example</a>
        </li>
        <li>
          <a href="#toc_common-questions">Common questions</a>
        