Multi part upload with asynko

gistfile1.cs

        public static IEnumerable<IAsync> Upload(string version, string config, byte[] content, byte[] thumbnail = null)
        {
            var multiPart = new MultiPartForm();
            multiPart.AddData("config", config);
            multiPart.AddFile("content", "application/octet-stream", content);
            if (thumbnail != null)
                multiPart.AddFile("thumbnail", "image/png", thumbnail);

            var url = MakeUrl("upload", version);
            var request = CreatePOSTRequest(url).Call<HttpWebRequest>();
            yield return request;
            request.Result.ContentType = multiPart.ContentType;
            var requestStream = request.Result.GetRequestStreamAsync().Call<Stream>();
            yield return requestStream;
            foreach (var part in multiPart.Parts)
            {
                yield return requestStream.Result.WriteAllAsync(part).Call<int>();
            }
            requestStream.Result.Close();
            var response = request.Result.GetResponseAsync().Call<HttpWebResponse>();
            yield return response;
            if (response.Result.StatusCode != HttpStatusCode.OK)
                throw new BadServerStatusException(response.Result.StatusCode);
            var responseStream = response.Result.GetResponseStream();
            if (responseStream == null)
                throw new NoResponseStreamException(response.Result);
            var reading = responseStream.ReadBytesToEndAsync().Call<byte[]>();
            yield return reading;
            var serverResponse = Serializer.Load<IServerResponse>(reading.Result);

            var fail = serverResponse as Fail;
            if (fail != null)
            {
                Log("Fail {0}: {1}.", fail.FailType, fail.Message);
                throw new FailResponseException(fail);            
            }

            var success = serverResponse as Success;
            if (success == null)
                throw new UnexpectedResponseException();

            yield return Async.Result(serverResponse);
        }