gistfile1.txt

 public class CollectionJsonContent : HttpContent
    {
        private readonly MemoryStream _memoryStream = new MemoryStream();
        public CollectionJsonContent(Collection collection)
        {
            var serializerSettings = new JsonSerializerSettings
                {
                    NullValueHandling = NullValueHandling.Ignore,
                    Formatting = Newtonsoft.Json.Formatting.Indented,
                    ContractResolver = new CamelCasePropertyNamesContractResolver()
                };

            using (var writer = new JsonTextWriter(new StreamWriter(_memoryStream)){CloseOutput = false})
            {
                var serializer = JsonSerializer.Create(serializerSettings);
                serializer.Serialize(writer,collection);
                writer.Flush();
            }
            _memoryStream.Position = 0;
        }


        protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
        {
            return _memoryStream.CopyToAsync(stream);
        }

        protected override bool TryComputeLength(out long length)
        {
            length = _memoryStream.Length;
            return true;
        }
    }