title: What are [HttpPost] and [ValidateAntiForgeryToken]
body: <p>When I use MVC 4, I see there are [HttpPost] and [ValidateAntiForgeryToken] at the top of some functions.</p>
  
  <pre><code>    [HttpPost]
      [ValidateAntiForgeryToken]
      public ActionResult PictureUpload(PictureModel model)
      {
       ....
      }
  </code></pre>
  
  <p>What are they???? What do this kind of expression call??? How to use them????</p>