C#（.net）multipart/form-data方式的post 服务端和客户端

public  string PostFileMessage(string strUrl, List postParaList)
        {
            try
            {
                string responseContent = "";
                var memStream = new MemoryStream();
                var webRequest = (HttpWebRequest)WebRequest.Create(strUrl);
                // 边界符
                var boundary = "---------------" + DateTime.Now.Ticks.ToString("x");
                // 边界符
                var beginBoundary = Encoding.ASCII.GetBytes("--" + boundary + "rn");
                // 最后的结束符
                var endBoundary = Encoding.ASCII.GetBytes("--" + boundary + "--rn");
                memStream.Write(beginBoundary, 0, beginBoundary.Length);
                // 设置属性
                webRequest.Method = "POST";
                webRequest.Timeout = 10000;
                webRequest.ContentType = "multipart/form-data; boundary=" + boundary;
                for (int i = 0; i < postParaList.Count; i++)
                {
                    PostDateClass temp = postParaList[i];
                    if (temp.Type == 1)
                    {
                        var fileStream = new FileStream(temp.Value, FileMode.Open, FileAccess.Read);
                        // 写入文件
                        const string filePartHeader =
                            "Content-Disposition: form-data; name="{0}"; filename="{1}"rn" +
                            "Content-Type: application/octet-streamrnrn";
                        var header = string.Format(filePartHeader, temp.Prop, temp.Value);
                        var headerbytes = Encoding.UTF8.GetBytes(header);
                        memStream.Write(headerbytes, 0, headerbytes.Length);
                        var buffer = new byte[1024];
                        int bytesRead; // =0
                        while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
                        {
                            memStream.Write(buffer, 0, bytesRead);
                        }
                        string end = "rn";
                        headerbytes = Encoding.UTF8.GetBytes(end);
                        memStream.Write(headerbytes, 0, headerbytes.Length);
                        fileStream.Close();
                    }
                    else if (temp.Type == 0)
                    {
                        // 写入字符串的Key
                        var stringKeyHeader = "Content-Disposition: form-data; name="{0}"" +
                                       "rnrn{1}rn";
                        var header = string.Format(stringKeyHeader, temp.Prop, temp.Value);
                        var headerbytes = Encoding.UTF8.GetBytes(header);
                        memStream.Write(headerbytes, 0, headerbytes.Length);
                    }
                    if (i != postParaList.Count - 1)
                        memStream.Write(beginBoundary, 0, beginBoundary.Length);
                    else
                        // 写入最后的结束边界符
                        memStream.Write(endBoundary, 0, endBoundary.Length);
                }
                webRequest.ContentLength = memStream.Length;
                var requestStream = webRequest.GetRequestStream();
                memStream.Position = 0;
                var tempBuffer = new byte[memStream.Length];
                memStream.Read(tempBuffer, 0, tempBuffer.Length);
                memStream.Close();
                requestStream.Write(tempBuffer, 0, tempBuffer.Length);
                requestStream.Close();
                using (HttpWebResponse res = (HttpWebResponse)webRequest.GetResponse())
                {

                    using (Stream resStream = res.GetResponseStream())
                    {
                        byte[] buffer = new byte[1024];
                        int read;
                        while ((read = resStream.Read(buffer, 0, buffer.Length)) > 0)
                        {
                            responseContent += Encoding.UTF8.GetString(buffer, 0, read);
                        }
                    }
                    res.Close();
                }
                return responseContent;
            }
            catch (Exception e)
            {
            }
            return null;


        }