WebClient multipart/form-data 文件上传

 public class HttpRequestClient
    {
        private ArrayList bytesArray;
        private Encoding encoding = Encoding.UTF8;
        private string boundary = String.Empty;

        public HttpRequestClient()
        {
            bytesArray = new ArrayList();
            string flag = DateTime.Now.Ticks.ToString("x");
            boundary = "---------------------------" + flag;
        }

        /// <summary>
        /// 合并请求数据
        /// </summary>
        /// <returns></returns>
        private byte[] MergeContent()
        {
            int length = 0;
            int readLength = 0;
            string endBoundary = "--" + boundary + "--
";
            byte[] endBoundaryBytes = encoding.GetBytes(endBoundary);

            bytesArray.Add(endBoundaryBytes);

            foreach (byte[] b in bytesArray)
            {
                length += b.Length;
            }

            byte[] bytes = new byte[length];

            foreach (byte[] b in bytesArray)
            {
                b.CopyTo(bytes, readLength);
                readLength += b.Length;
            }

            return bytes;
        }

        /// <summary>
        /// 上传
        /// </summary>
        /// <param name="requestUrl">请求url</param>
        /// <param name="responseText">响应</param>
        /// <returns></returns>
        public bool Upload(String requestUrl, out String responseText)
        {
            WebClient webClient = new WebClient();
            webClient.Headers.Add("Content-Type", "multipart/form-data; boundary=" + boundary);
            responseText = string.Empty;
            byte[] responseBytes;
            byte[] bytes = MergeContent();

            try
            {
                //responseText = requestUrl;//+ "requestUrl---   "    + bytes == null ? "error null" : bytes.Length.ToString();
                //return true;
                responseBytes = webClient.UploadData(requestUrl, bytes);

                responseText = System.Text.Encoding.UTF8.GetString(responseBytes);

            }
            catch (Exception ex)
            {
                throw ex;
                //responseText = ex.Message;
                //return false;
                //Stream responseStream = ex.Response.GetResponseStream();
                //responseBytes = new byte[ex.Response.ContentLength];
                //responseStream.Read(responseBytes, 0, responseBytes.Length);
            }
            responseText = System.Text.Encoding.UTF8.GetString(responseBytes);
            return false;
        }

        /// <summary>
        /// 设置表单数据字段
        /// </summary>
        /// <param name="fieldName">字段名</param>
        /// <param name="fieldValue">字段值</param>
        /// <returns></returns>
        public void SetFieldValue(String fieldName, String fieldValue)
        {
            string httpRow = "--" + boundary + "
Content-Disposition: form-data; name="{0}"

{1}
";
            string httpRowData = String.Format(httpRow, fieldName, fieldValue);

            bytesArray.Add(encoding.GetBytes(httpRowData));
        }

        /// <summary>
        /// 设置表单文件数据
        /// </summary>
        /// <param name="fieldName">字段名</param>
        /// <param name="filename">字段值</param>
        /// <param name="contentType">内容内型</param>
        /// <param name="fileBytes">文件字节流</param>
        /// <returns></returns>
        public void SetFieldValue(String fieldName, String filename, String contentType, Byte[] fileBytes)
        {
            string end = "
";
            string httpRow = "--" + boundary + "
Content-Disposition: form-data; name="{0}"; filename="{1}"
Content-Type: {2}

";
            string httpRowData = String.Format(httpRow, fieldName, filename, contentType);

            byte[] headerBytes = encoding.GetBytes(httpRowData);
            byte[] endBytes = encoding.GetBytes(end);
            byte[] fileDataBytes = new byte[headerBytes.Length + fileBytes.Length + endBytes.Length];

            headerBytes.CopyTo(fileDataBytes, 0);
            fileBytes.CopyTo(fileDataBytes, headerBytes.Length);
            endBytes.CopyTo(fileDataBytes, headerBytes.Length + fileBytes.Length);

            bytesArray.Add(fileDataBytes);
        }
    }

        /// <summary>
        /// 上传图片 返回空上传失败
        /// </summary>
        /// <param name="posturl"></param>
        /// <param name="userid"></param>
        /// <param name="filename"></param>
        /// <param name="dir"></param>
        /// <param name="data"></param>
        /// <returns></returns>
        public static string UpLoadFile(string posturl, int userid, string filename, string dir, byte[] data)
        {
            string result = string.Empty; 
            try
            { 
                var httpRequestClient = new HttpRequestClient();

                httpRequestClient.SetFieldValue("userId", userid.ToString());
                httpRequestClient.SetFieldValue("upFile", filename, "application/octet-stream", data);
                httpRequestClient.SetFieldValue("dir", dir);


                httpRequestClient.Upload(posturl, out result);
                //return result;
                UploadImg img = Newtonsoft.Json.JsonConvert.DeserializeObject<UploadImg>(result);

                if (img.state.ToUpper() == "SUCCESS")
                {
                    return ConfigHelper.GetImageDomain() + img.url;
                    //imgUrlList.Add("http://img.zhijia.com" + uploadResult.url);
                    // imgUrlList.Add(WebConfig.ImgLink + uploadResult.url);
                }
                return result;
            }
            catch (Exception ex)
            {
                throw ex;
                //return "error:" + JsonConvert.SerializeObject(ex) + result;
                //return string.Empty;
            }
            //  img.state=
        }

 　　　　　　　　string files = request.Head;　　　　//用户头像
                if (Request.Files != null && Request.Files.Count() > 0)
                {
                    var reqFile = Request.Files[0];
                    var fileBytes = new byte[reqFile.ContentLength];
                    reqFile.InputStream.Read(fileBytes, 0, (int)reqFile.ContentLength);
                    var fileName = RequestInfo.UserId + reqFile.FileName; //+ AppApi.Helper.Function.GetExtensionName(fileBytes);

                    files = AppApi.Helper.Function.UpLoadFile(AppApi.Helper.ConfigHelper.GetImageFileService(), RequestInfo.UserId, fileName, AppApi.Helper.ConfigHelper.GetHeadDIR(), fileBytes);
                }