我的结果如下所示：

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;
              }
          }
     }
}