多文件多参数中转客户端（转卢震的）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.IO;
using System.Collections.Specialized;

namespace Controller.Interface.Area
{

    public class Client
    {

        public static string UploadFileEx( string url,
            List<Stream> fileStream, NameValueCollection querystring
            )
        {
            string boundary = "----------" + DateTime.Now.Ticks.ToString("x");
            HttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create(new Uri(url));
            webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
            webrequest.Method = "POST";
            StringBuilder sb = new StringBuilder();
            sb.Append("--");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Disposition: form-data; name=\"");
            sb.Append("piaoClient");
            sb.Append("\"; filename=\"");
            sb.Append("piaoClient");
            sb.Append("\"");
            sb.Append("\r\n");
            sb.Append("Content-Type: ");
            sb.Append(contenttype);
            sb.Append("\r\n");
            sb.Append("\r\n");
            StringBuilder sb1 = new StringBuilder();
            foreach (var key in querystring.Keys)
            {
                sb1.Append("--");
                sb1.Append(boundary);
                sb1.Append("\r\n");
                sb1.Append("Content-Disposition: form-data; name=\""+key.ToString()+"\"");
                sb1.Append("\r\n");
                sb1.Append("\r\n");
                sb1.Append(querystring[key.ToString()].ToString());
                sb1.Append("\r\n");
            }
            byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sb.ToString());
            byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
            byte[] postDate = Encoding.UTF8.GetBytes(sb1.ToString());
            long length = postHeaderBytes.Length * fileStream.Count + fileStream.Sum(s1 => s1.Length) + (boundaryBytes.Length * fileStream.Count) + postDate.Length;
            webrequest.ContentLength = length;
            Stream requestStream = webrequest.GetRequestStream();
            requestStream.Write(postDate, 0, postDate.Length);
            foreach (var filestream1 in fileStream)
            {
                requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
                byte[] buffer = new Byte[checked((uint)Math.Min(4096, (int)filestream1.Length))];
                int bytesRead = 0;
                while ((bytesRead = filestream1.Read(buffer, 0, buffer.Length)) != 0)
                    requestStream.Write(buffer, 0, bytesRead);
                requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);
            }
            webrequest.Timeout = 1000000;
            WebResponse responce = webrequest.GetResponse();
            Stream s = responce.GetResponseStream();
            StreamReader sr = new StreamReader(s);
            string str = sr.ReadToEnd();
            foreach (var filestream1 in fileStream)
            {
                filestream1.Close();
            }
            requestStream.Close();
            sr.Close();
            s.Close();
            responce.Close();
            return str;
        }
    }
}