title: Return custom HTTP code from ActionFilterAttribute
body: <p>I use the code below to throttle my ASP.NET Web Api:</p>
  
  <pre><code>public class Throttle : ActionFilterAttribute
  {
      public override async Task OnActionExecutingAsync(HttpActionContext context, CancellationToken cancellationToken)
      {
              // ...
              if (throttle)
              {
                  throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.Conflict));
              }
      }
  }
  </code></pre>
  
  <p>However, I cannot return error code 429, because it's not in HttpStatusCode enum. Is there a way to return a custom error code?</p>