gistfile1.txt

public static class FormatterCollectionExtensions
    {

        public static Tuple<MediaTypeFormatter,MediaTypeHeaderValue> Negotiate<T>(this MediaTypeFormatterCollection formatters, HttpRequestMessage requestMessage)
        {
            var formatSelector = new FormatterSelector();
            MediaTypeHeaderValue mediaType = null;
            var response = new HttpResponseMessage() {RequestMessage = requestMessage};
            var formatter = formatSelector.SelectWriteFormatter(typeof(T), new FormatterContext(response, false), formatters, out mediaType);
            return new Tuple<MediaTypeFormatter, MediaTypeHeaderValue>(formatter,mediaType);
        }
    }


     public HttpResponseMessage Get() {
            var response = new HttpResponseMessage();

            var contact = new Contact() {FirstName = "Joe", LastName = "Brown"};
            
            var mediaInfo = Configuration.Formatters.Negotiate<Contact>(Request);
            
            response.Content = new SimpleObjectContent<Contact>(contact, mediaInfo.Item1);
            response.Content.Headers.ContentType = mediaInfo.Item2;

            return response;
        }