POST http://pic.kuche.com/postpic/upload?flash=1 HTTP/1.1
Host: pic.kuche.com
Connection: keep-alive
Content-Length: 198248
Origin: http://pic2.58.com
file-extensions: jpg
pic-isaddwaterpic: True
pic-path: /p1/big/
pic-size: 640*640
User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
content-type: application/octet-stream
pic-dpi: 0
pic-cut: 0*0*0*0
pic-bulk: 0
pic-name: /p1/tiny/
Accept: */*
Referer: http://pic2.58.com/ui7/post/PictureUpload_zip_s1.swf
Accept-Encoding: gzip,deflate,sdch
Accept-Language: zh-CN,zh;q=0.8
Accept-Charset: GBK,utf-8;q=0.7,*;q=0.3
Fiddler-Encoding: base64

上边是表头文件
下边是提交的附件Request Body，其实就是一个Base64的字符串，为了简化页面，没有全部copy上来。


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

 private void PostFileTo58()
        {
//文件 
            FileStream fileStream = new FileStream(@"C:\Users\Public\Pictures\Sample Pictures\Koala.jpg", FileMode.Open, FileAccess.Read);
            string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
            //请求 
            WebRequest req = WebRequest.Create(@"http://pic.kuche.com/postpic/upload?flash=1");
            req.Method = "POST";
            req.ContentType = "multipart/form-data; boundary=" + boundary;
            //组织表单数据 
            StringBuilder sb = new StringBuilder();
            sb.Append("Host: pic.kuche.com");
            sb.Append("\r\n");
            sb.Append("Connection: keep-alive");
            sb.Append("\r\n");
            sb.Append("Content-Length: 296386");
            sb.Append("\r\n");
            sb.Append("Origin: http://pic2.58.com");
            sb.Append("\r\n");
            sb.Append("file-extensions: jpg");
            sb.Append("\r\n");
            sb.Append("pic-isaddwaterpic: True");
            sb.Append("\r\n");
            sb.Append("pic-path: /p1/big/");
            sb.Append("\r\n");
            sb.Append("pic-size: 640*640");
            sb.Append("\r\n");
            sb.Append("User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1");
            sb.Append("\r\n");
            sb.Append("content-type: application/octet-stream");
            sb.Append("\r\n");
            sb.Append("pic-dpi: 0");
            sb.Append("\r\n");
            sb.Append("pic-cut: 0*0*0*0");
            sb.Append("\r\n");
            sb.Append("pic-bulk: 0");
            sb.Append("\r\n");
            sb.Append("pic-name: /p1/tiny/");
            sb.Append("\r\n");
            sb.Append("Accept: */*");
            sb.Append("\r\n");
            sb.Append("Referer: http://pic2.58.com/ui7/post/PictureUpload_zip_s1.swf");
            sb.Append("\r\n");
            sb.Append("Accept-Encoding: gzip,deflate,sdch");
            sb.Append("\r\n");
            sb.Append("Accept-Language: zh-CN,zh;q=0.8");
            sb.Append("\r\n");
            sb.Append("Accept-Charset: GBK,utf-8;q=0.7,*;q=0.3");
            sb.Append("\r\n");
            //sb.Append("Fiddler-Encoding: base64");
            sb.Append("\r\n\r\n");
            string head = sb.ToString();
            byte[] form_data = Encoding.UTF8.GetBytes(head);
            //结尾 
            byte[] foot_data = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");
          
            //post总长度 
            long length = form_data.Length + fileStream.Length + foot_data.Length;
            req.ContentLength = length;

            Stream requestStream = req.GetRequestStream();
            //发送表单参数 
            requestStream.Write(form_data, 0, form_data.Length);
            //文件内容 
            byte[] buffer = new Byte[checked((uint)Math.Min(4096, (int)fileStream.Length))];
            int bytesRead = 0;
            while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
                requestStream.Write(buffer, 0, bytesRead);


            byte[] bytes = buffer;
            MemoryStream ms = new MemoryStream(bytes);
            ms.Position = 0;
            System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
            ms.Close();


            //结尾 
            requestStream.Write(foot_data, 0, foot_data.Length);
            requestStream.Close();
            string result = string.Empty;
            WebResponse wresp = null;
            try
            {
                wresp = req.GetResponse();
                Stream stream2 = wresp.GetResponseStream();
                StreamReader reader2 = new StreamReader(stream2);

                result = reader2.ReadToEnd();
            }
            catch (Exception ex)
            {
                if (wresp != null)
                {
                    wresp.Close();
                    wresp = null;
                }
            }
            finally
            {
                req = null;
            }

        }