C# HttpClient 4.5 multipart/form-data upload

my result looks like this:

public static async Task<string> Upload(byte[] image)
     using (var client = new HttpClient())
         using (var content =
             new MultipartFormDataContent("Upload----" + DateTime.Now.ToString(CultureInfo.InvariantCulture)))
             content.Add(new StreamContent(new MemoryStream(image)), "bilddatei", "upload.jpg");

              using (
                 var message =
                     await client.PostAsync("http://www.directupload.net/index.php?mode=upload", content))
                  var input = await message.Content.ReadAsStringAsync();

                  return !string.IsNullOrWhiteSpace(input) ? Regex.Match(input, @"http://\w*\.directupload\.net/images/\d*/\w*\.[a-z]{3}").Value : null;

It works more or less like this (example using an image/jpg file):

async public Task<HttpResponseMessage> UploadImage(string url, byte[] ImageData)
    var requestContent = new MultipartFormDataContent(); 
    //    here you can specify boundary if you need---^
    var imageContent = new ByteArrayContent(ImageData);
    imageContent.Headers.ContentType = 

    requestContent.Add(imageContent, "image", "image.jpg");

    return await client.PostAsync(url, requestContent);

(You can requestContent.Add() whatever you want, take a look at the HttpContent descendant to see available types to pass in)

When completed, you'll find the response content inside HttpResponseMessage.Content that you can consume with HttpContent.ReadAs*Async.

This is an example of how to post string and file stream with HTTPClient using MultipartFormDataContent. The Content-Disposition and Content-Type need to be specified for each HTTPContent:

Here's my example. Hope it helps:

private static void Upload()
    using (var client = new HttpClient())
        client.DefaultRequestHeaders.Add("User-Agent", "CBS Brightcove API Service");

        using (var content = new MultipartFormDataContent())
            var path = @"C:\B2BAssetRoot\files\596086\596086.1.mp4";

            string assetName = Path.GetFileName(path);

            var request = new HTTPBrightCoveRequest()
                    Method = "create_video",
                    Parameters = new Params()
                            CreateMultipleRenditions = "true",
                            EncodeTo = EncodeTo.Mp4.ToString().ToUpper(),
                            Token = "x8sLalfXacgn-4CzhTBm7uaCxVAPjvKqTf1oXpwLVYYoCkejZUsYtg..",
                            Video = new Video()
                                    Name = assetName,
                                    ReferenceId = Guid.NewGuid().ToString(),
                                    ShortDescription = assetName

            //Content-Disposition: form-data; name="json"
            var stringContent = new StringContent(JsonConvert.SerializeObject(request));
            stringContent.Headers.Add("Content-Disposition", "form-data; name=\"json\"");
            content.Add(stringContent, "json");

            FileStream fs = File.OpenRead(path);

            var streamContent = new StreamContent(fs);
            streamContent.Headers.Add("Content-Type", "application/octet-stream");
            //Content-Disposition: form-data; name="file"; filename="C:\B2BAssetRoot\files\596090\596090.1.mp4";
            streamContent.Headers.Add("Content-Disposition", "form-data; name=\"file\"; filename=\"" + Path.GetFileName(path) + "\"");
            content.Add(streamContent, "file", Path.GetFileName(path));

            //content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");

            Task<HttpResponseMessage> message = client.PostAsync("http://api.brightcove.com/services/post", content);

            var input = message.Result.Content.ReadAsStringAsync();