[c#] multipart-form upload datoteke

CookieContainer cookies = new CookieContainer();
NameValueCollection querystring = new NameValueCollection();
querystring["uname"] = "Dodo";
String uploadfile;
uploadfile = "M:\\slike\\slika.jpg";
String outdata = UploadFileEx(uploadfile, "http://www.spletnastran.si/test.php", "filename", "image/jpeg", querystring, cookies);
MessageBox.Show(outdata);


public static string UploadFileEx(string uploadfile, string url, string fileFormName, string contenttype, NameValueCollection querystring, CookieContainer cookies)
        {
            if ((fileFormName == null) ||
                (fileFormName.Length == 0))
            {
                fileFormName = "file";
            }

            if ((contenttype == null) ||
                (contenttype.Length == 0))
            {
                contenttype = "application/octet-stream";
            }

            string postdata;
            postdata = "?";
            if (querystring != null)
            {
                foreach (string key in querystring.Keys)
                {
                    postdata += key + "=" + querystring.Get(key) + "&";
                }
            }
            Uri uri = new Uri(url + postdata);

            string boundary = "----------" + DateTime.Now.Ticks.ToString("x");
            HttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create(uri);
            webrequest.CookieContainer = cookies;
            webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
            webrequest.Method = "POST";


            // Build up the post message header
            StringBuilder sb = new StringBuilder();

            sb.Append("--");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Disposition: form-data; name=\"");
            sb.Append(fileFormName);
            sb.Append("\"; filename=\"");
            sb.Append(Path.GetFileName(uploadfile));
            sb.Append("\"");
            sb.Append("\r\n");
            sb.Append("Content-Type: ");
            sb.Append(contenttype);
            sb.Append("\r\n");
            sb.Append("\r\n");

            string postHeader = sb.ToString();
            byte[] postHeaderBytes = Encoding.UTF8.GetBytes(postHeader);

            // Build the trailing boundary string as a byte array
            // ensuring the boundary appears on a line by itself
            byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");

            FileStream fileStream = new FileStream(uploadfile, FileMode.Open, FileAccess.Read);
            long length = postHeaderBytes.Length + fileStream.Length + boundaryBytes.Length;
            webrequest.ContentLength = length;

            Stream requestStream = webrequest.GetRequestStream();

            // Write out our post header
            requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);

            // Write out the file contents
            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);

            // Write out the trailing boundary
            requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);
            WebResponse responce = webrequest.GetResponse();
            Stream s = responce.GetResponseStream();
            StreamReader sr = new StreamReader(s);

            return sr.ReadToEnd();
        }