title: How do you throw HttpResponseException in ASP 5 (vnext)
body: <p>I'm writing an api controller in ASP 5. I want to return a bad request code exception if the parameters passed to the service are incorrect. In the current version of webapi I would do:</p>
  
  <pre><code>throw new HttpResponseException(HttpStatusCode.BadRequest);
  </code></pre>
  
  <p>However <code>HttpResponseException</code> is part of <code>System.Web</code>, which has been removed from ASP 5 and thus I cannot instantiate it anymore. </p>
  
  <p>What is the proper way to do this in vNext?</p>