title: With Compression ActionFilter, Server error messages clears content-encoding header and renders as gibberish
body: <p>When I'm using a compression filter and get an error, the error page is just gibberish characters. The problem seems to be that when IIS transfers to the error page the compression filter is still in effect, but the headers are cleared. Without the "Content-encoding: gzip" header the browser just displays the raw gzipped binary data.</p>
  
  <p>I'm using IIS7.5, ASP.NET MVC 2 Preview 2 and an ActionFilter that looks like this:</p>
  
  <pre><code>public class CompressResponseAttribute : ActionFilterAttribute
  {
      public override void OnActionExecuting(ActionExecutingContext filterContext)
      {
          var request = filterContext.HttpContext.Request;
          var response = filterContext.HttpContext.Response;
  
          var acceptEncoding = request.Headers["Accept-Encoding"];
  
          if (string.IsNullOrEmpty(acceptEncoding))
              return;
  
          acceptEncoding = acceptEncoding.ToLowerInvariant();
  
          if (acceptEncoding.Contains("gzip"))
          {
              response.AppendHeader("Content-encoding", "gzip");
              response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
          }
          else if (acceptEncoding.Contains("deflate"))
          {
              response.AppendHeader("Content-encoding", "deflate");
              response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
          }
      }
  }
  </code></pre>
  
  <p>Anyone else experienced this?</p>