title: BeginForm with null controller and action missing parameters
body: <p>I want to add an ID attribute to my form, so I follow the answer <a href="https://stackoverflow.com/questions/216600/html-beginform-and-adding-properties">here</a></p>
  
  <p>Originally my code was using:</p>
  
  <pre><code>Html.BeginForm()
  </code></pre>
  
  <p>and the output looks like this:</p>
  
  <pre><code>&lt;form action="/Controller/Action?Id=5" method="post"&gt;
  </code></pre>
  
  <p>but when I replace the Html.BeginForm() with:</p>
  
  <pre><code>Html.BeginForm(null, null, FormMethod.Post, new { @Id = "blah" });
  </code></pre>
  
  <p>the output form is missing the parameter:</p>
  
  <pre><code>&lt;form action="/Controller/Action" method="post"&gt;
  </code></pre>
  
  <p>It all seems to just work "magically" if I replace the BeginForm with <code>&lt;form action="" method="post"&gt;</code> but I'd like to understand what's going wrong with the helper version.</p>