title: Input type file, required attribute not working
body: <p>I am using the MVC 4 framework in my C# project.
  I made a page that add ads in my DB (path) and the actual
  image in a folder.</p>
  
  <p>The code works but I want to build a safety mechanism that prevents
  the page from posting the empty input file (image selector).
  I found out that HTML 5 supports the "required" attribute but I still have
  some problems left.</p>
  
  <p>When I press the submit button (when there is no image selected)  it marks
  the field but the code behind (UploadAd method in UploadController) is still fired.
  What is causing this?</p>
  
  <p>Following images and code could make it easier to understand:</p>
  
  <p>View code: <a href="http://pastebin.com/s9eWn4zW" rel="nofollow">http://pastebin.com/s9eWn4zW</a></p>
  
  <p>Controller code + site validation: <a href="http://oi47.tinypic.com/23leeef.jpg" rel="nofollow">http://oi47.tinypic.com/23leeef.jpg</a></p>