无法在asp.net mvc中实现将tweet和图像一起发送到twitter

我正在开发asp.net mvc。我正在尝试实现推特撰写推特机制文本和图像，并将其作为推特在推特中发送。我遵循了twitter API 1.1提供的文档。我遵循Twitterizer库来完成这一步，但它给我带来了错误，就像API版本1被弃用一样，尽管我使用的是最新的版本，它适用于除此之外的其他端点。所以我决定在我自己的上发出http请求

在我的情况下，我的表单中有文本区域和文件上传控件，比如

<form method="post" action="/Home/Upload" enctype="multipart/form-data">
<textarea id="message" name="message"></textarea>
<input type="file" name="file"/>
<input type="submit" value="submit"/>
</form>

之后，在我的动作中，我得到了用户选择的图像和他在我的操作中输入的文本。我已经将HttpPostedPostedFileBase转换为类似字节[]的

[HttpPost]
        public ActionResult Upload(FormCollection coll, HttpPostedFileBase upfile)
        {
            byte[] data;
            using (Stream inputStream = upfile.InputStream)
            {
                MemoryStream memoryStream = inputStream as MemoryStream;
                if (memoryStream == null)
                {
                    memoryStream = new MemoryStream();
                    inputStream.CopyTo(memoryStream);
                }
                data = memoryStream.ToArray();
            }
            HttpWebRequest webRequest = WebRequest.Create("https://api.twitter.com/1.1/statuses/update_with_media.json") as HttpWebRequest;
            OAuthBase oauth = new OAuthBase();
            string nonce = oauth.GenerateNonce();
            string timeStamp = oauth.GenerateTimeStamp();
            string normalizedUrl;
            string normalizedRequestParameters;
            string sig = oauth.GenerateSignature
            (new System.Uri("https://api.twitter.com/1.1/statuses/update_with_media.json"), consumerKey, consumerSecret, userinfo.AuthToken,
            userinfo.PayUserId, "POST", timeStamp, nonce,
            OAuthBase.SignatureTypes.HMACSHA1, out normalizedUrl,
            out normalizedRequestParameters);
            string header = string.Format(@"OAuth oauth_consumer_key=""{0}"",oauth_signature_method=""{1}"",oauth_timestamp=""{2}"",oauth_nonce=""{3}"",oauth_version=""{4}"",oauth_token=""{5}"",oauth_signature=""{6}""",
            HttpUtility.UrlEncode(consumerKey), HttpUtility.UrlEncode("HMAC-SHA1"), HttpUtility.UrlEncode(timeStamp), HttpUtility.UrlEncode(nonce), HttpUtility.UrlEncode("1.0"), HttpUtility.UrlEncode(userinfo.AuthToken), HttpUtility.UrlEncode(sig));
            webRequest.Headers.Add("Authorization", header);
            webRequest.Method = "POST";
            webRequest.Credentials = CredentialCache.DefaultCredentials;
            ((HttpWebRequest)webRequest).UserAgent = ".NET Framework Example Client";
            Dictionary<string, object> fieldsToInclude = new Dictionary<string, object>();
            fieldsToInclude.Add("status", coll["new_message"]);
            fieldsToInclude.Add("media[]", data);
            string boundary = Guid.NewGuid().ToString().Replace("-", "");
            string dataBoundary = "--------------------r4nd0m";
            string contentType = "multipart/form-data; boundary=" + dataBoundary;
            byte[] mydata = GetMultipartFormData(fieldsToInclude, contentType);
            webRequest.ContentLength = mydata.Length;
            webRequest.ContentType = contentType;
            using (Stream requestStream = webRequest.GetRequestStream())
            {
                if (mydata != null)
                {
                    requestStream.Write(mydata, 0, mydata.Length);
                }
            }
            using (HttpWebResponse webResponse = webRequest.GetResponse() as HttpWebResponse)
            {
                StreamReader reader = new StreamReader(webResponse.GetResponseStream());
                string retVal = reader.ReadToEnd();
            }        
            return View();
        }

在这里，我写了一种为图像和文本数据准备多部分形式数据结构的方法，比如

private byte[] GetMultipartFormData(Dictionary<string, object> fieldsToInclude, string boundary)
        {
            Stream formDataStream = new MemoryStream();
            Encoding encoding = Encoding.UTF8;          
            foreach (KeyValuePair<string, object> kvp in fieldsToInclude)
            {
                if (kvp.Value.GetType() == typeof(byte[]))
                {   //assume this to be a byte stream
                    byte[] data = (byte[])kvp.Value;
                    string header = string.Format("--{0}'r'nContent-Disposition: form-data; name='"{1}'"; filename='"{2}'";'r'nContent-Type: application/octet-stream'r'n'r'n",
                        boundary,
                        kvp.Key,
                        kvp.Key);
                    byte[] headerBytes = encoding.GetBytes(header);
                    formDataStream.Write(headerBytes, 0, headerBytes.Length);
                    formDataStream.Write(data, 0, data.Length);

                }
                else
                {   //this is normal text data
                    string header = string.Format("--{0}'r'nContent-Disposition: form-data; name='"{1}'"'r'n'r'n{2}'r'n",
                        boundary,
                        kvp.Key,
                        kvp.Value);
                    byte[] headerBytes = encoding.GetBytes(header);
                    formDataStream.Write(headerBytes, 0, headerBytes.Length);
                }
            }
            string footer = string.Format("'r'n--{0}--'r'n", boundary);
            formDataStream.Write(encoding.GetBytes(footer), 0, footer.Length);
            formDataStream.Position = 0;
            byte[] returndata = new byte[formDataStream.Length];
            formDataStream.Read(returndata, 0, returndata.Length);
            formDataStream.Close();
            return returndata;
        }

这是我下面的方式，以http请求上传图片到twitter（又称为媒体上传）。但我收到错误500内部服务器错误。如果我的手术出错，请指导我。