using (var reqConts = new MultipartFormDataContent())

{

    for (int i = ; i < colletion.Count; i++)

    {

        HttpPostedFileBase file = colletion[i];

        string extName = Path.GetExtension(file.FileName);

        string fileName = Guid.NewGuid().ToString() + extName;

        var stream = new StreamReader(file.InputStream).BaseStream;

        var streamCont = new StreamContent(stream);

        streamCont.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data");//image/*

        streamCont.Headers.ContentLength = stream.Length;

        reqConts.Add(streamCont, "image_binary" + i, fileName);

    }

    var respone = client.PostAsync(uploadUrl, reqConts).Result.Content.ReadAsStringAsync();

    var res = respone.Result;

    Basics.LogFun.Instance().WriteLog(LogFunType.SystemErrLog, "接收发送请求结果：" + res);

    JsonSerializer serializer = new JsonSerializer();

    using (var jsonReader = new JsonTextReader(new StringReader(respone.Result)))

    {

        Result crrresult = serializer.Deserialize<Result>(jsonReader);

        if (crrresult.Success) {

            return Content(ReturnMessage(true, "处理成功"));

        }

    }

}

private string postFile(HttpFileCollectionBase httpFileCollection, string postUrl)

        {

            string encrypt = "f933797503d6e2c36762428a280e0559";

            string boundary = "";

            #region 定义请求体中的内容 并转成二进制

            string Enter = "\r\n";

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(postUrl);

            request.Method = "POST";

            request.ContentType = "multipart/form-data;boundary=--------------------------" + boundary;

            request.Accept = "*/*";

            Stream myRequestStream = request.GetRequestStream();//定义请求流

            for (int i = ; i < httpFileCollection.Count; i++)

            {

                HttpPostedFileBase file = httpFileCollection[i];

                string extName = Path.GetExtension(file.FileName);

                string fileName = Guid.NewGuid().ToString() + extName;

                Stream fileStream = file.InputStream;

                byte[] fileContentByte = new byte[fileStream.Length]; // 文件内容二进制

                fileStream.Read(fileContentByte, , fileContentByte.Length);

                fileStream.Close();

                string fileContentStr = Enter + "----------------------------" + boundary + Enter

                   + "Content-Type:image/*" + Enter

                   + "Content-Disposition: form-data; name=\"image_binary" + i.ToString() + "\"; filename=\"" + fileName + "\"" + Enter + Enter;

                var fileContentStrByte = Encoding.UTF8.GetBytes(fileContentStr);//fileContent一些名称等信息的二进制（不包含文件本身）

                myRequestStream.Write(fileContentStrByte, , fileContentStrByte.Length);

                myRequestStream.Write(fileContentByte, , fileContentByte.Length);

            }

            string encryptStr = Enter + "----------------------------" + boundary + Enter

                    + "Content-Disposition: form-data; name=\"encrypt\"" + Enter + Enter

                    + encrypt + Enter + "--" + boundary + "--";

            var encryptStrByte = Encoding.UTF8.GetBytes(encryptStr);//encrypt所有字符串二进制

            myRequestStream.Write(encryptStrByte, , encryptStrByte.Length);

            #endregion

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();//发送

            Stream myResponseStream = response.GetResponseStream();//获取返回值

            StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));

            string retString = myStreamReader.ReadToEnd();

            myStreamReader.Close();

            myResponseStream.Close();

            return retString;

        }