gistfile1.cs

    public class LoggingFormatterSelector : IFormatterSelector
    {
        private readonly FormatterSelector _FormatterSelector = new FormatterSelector();


        public new MediaTypeFormatter SelectReadFormatter(Type type, FormatterContext formatterContext, IEnumerable<MediaTypeFormatter> formatters)
        {
            string descriptFormatterContext = GetDescriptFormatterContext(formatterContext);

            Console.WriteLine("Selecting Read Formatter for type {0} based on formatter context: {1}", type.Name, descriptFormatterContext);
            var mediaTypeFormatter = _FormatterSelector.SelectReadFormatter(type, formatterContext, formatters);
            Console.WriteLine("Selected Read Formatter : {0}", mediaTypeFormatter.GetType().Name);
            return mediaTypeFormatter;
        }


        public new MediaTypeFormatter SelectWriteFormatter(Type type, FormatterContext formatterContext, IEnumerable<MediaTypeFormatter> formatters, out MediaTypeHeaderValue mediaType)
        {
            string descriptFormatterContext = GetDescriptFormatterContext(formatterContext);

            Console.WriteLine("Selecting Write Formatter for type {0} based on formatter context: {1}", type.Name, descriptFormatterContext);
            var mediaTypeFormatter = _FormatterSelector.SelectWriteFormatter(type, formatterContext, formatters, out mediaType);
            Console.WriteLine("Selected Write Formatter : {0} {1}", mediaTypeFormatter.GetType().Name, mediaType);
            return mediaTypeFormatter;
        }


        private string GetDescriptFormatterContext(FormatterContext formatterContext)
        {
            return String.Format("ContentType {0}, HasRequest {1}, HasResponse {2}, IsRead {3} ",
                            formatterContext.ContentType , 
                            formatterContext.Request != null,
                            formatterContext.Response != null, 
                            formatterContext.IsRead);
        }

    }
}

Which can be plugged in like this,

    config.ServiceResolver.SetService(typeof(IFormatterSelector),new LoggingFormatterSelector());