error when uploading image to fastpic.ru by C#

[sergio090588]

Hi
I want to upload image to fastpic.ru
this is my code:

public string UploadImageToFastPic(string uploadfile, string url,string fileFormName, string contenttype)
        {
            if ((fileFormName == null) || (fileFormName.Length == 0))
            {
                fileFormName = "file";
            }
 
            if ((contenttype == null) || (contenttype.Length == 0))
            {
                contenttype = "application/octet-stream";
            }
 
            string boundary = "------WebKitFormBoundary" + DateTime.Now.Ticks.ToString("x");
 
            HttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create(url);
            webrequest.CookieContainer = new CookieContainer();
            webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
            webrequest.Method = "POST";
 
 
            // Build up the post message header
            StringBuilder sb = new StringBuilder();
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-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");
 
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"check_thumb\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("size");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"thumb_text\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("Увеличить");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"thumb_size\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("170");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"res_select\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("500");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"orig_resize\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("500");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"orig_rotate\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("0");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"jpeg_quality\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("75");
            sb.Append(boundary);
            sb.Append("Content-Dis-data; name=\"submit\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("Загрузить");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("\r\n");
            sb.Append("Content-Dis-data; name=\"uploading\"");
            sb.Append("\r\n");
            sb.Append("\r\n");
 
            sb.Append("1");
            sb.Append("\r\n");
            sb.Append(boundary);
            sb.Append("--");
 
            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();
 

this is my code at from main:

richTextBox_FullStory.Text = pro.UploadImageToFastPic("E:\\The Haves.jpg","fastpic.ru/uploadmulti", "file[]", "image/jpeg");

I want return result when done function UploadImageToFastpic is content of file .html uploaded file image succussfully

but when function UploadImageToFastpic finished so result return still content of file .html when not uploaded image to fastpic.ru yet

I debug and I realize can't get cookies

SOMEBODY HELP ME, PLEASE !!!!

P/s: the first enter click to fastpic.ru that it appear popup.I don't know thing influence to my code

thank you so much for your help !!!!!!!!!!!