C# HttpWebRequest向远程地址Post文件

HttpWebRequest向远程地址Post文件

        /// <summary>
        /// 上传文件到远程服务器
        /// </summary>
        /// <param name="url">远程服务器接收Api</param>
        /// <param name="postStream">文件流</param>
        /// <param name="contentType">内容类型默认application/octet-stream</param>
        /// <returns></returns>
        static public string PostFileByHttpWebRequest(string url, Stream postStream, string contentType = "application/octet-stream")
        {
            string result = string.Empty;
            HttpWebRequest request = null;
            try
            {
                ServicePointManager.DefaultConnectionLimit = int.MaxValue;
                request = (HttpWebRequest)WebRequest.Create(url);
                request.Timeout = 50000;
                request.Method = "POST";
                request.ContentType = contentType;
                request.ContentLength = postStream.Length;

                using (Stream writer = request.GetRequestStream())
                {
                    WriteTo(postStream, writer, postStream.Length);
                }
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {
                    using (StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
                    {
                        result = reader.ReadToEnd();
                    }
                }
            }
            catch (WebException ex)
            {
                request.Abort();
                result = ex.Message.ToString();
            }
            catch (Exception ex)
            {
                request.Abort();
                result = ex.Message.ToString();
            }
            finally
            {
                if (request != null)
                {
                    request.Abort();
                }
            }
            return result;
        }

        static private long WriteTo(Stream orignStream, Stream destStream, long totalSize)
        {
            int BufferSize = 4 * 1024;

            var buffer = new byte[BufferSize];

            long alreadyRead = 0;
            while (alreadyRead < totalSize)
            {
                var readSize = orignStream.Read(buffer, 0, BufferSize);
                if (readSize <= 0)
                    break;

                if (alreadyRead + readSize > totalSize)
                    readSize = (int)(totalSize - alreadyRead);
                alreadyRead += readSize;
                destStream.Write(buffer, 0, readSize);
            }
            destStream.Flush();

            return alreadyRead;
        }