C# - Can't Upload File Http With Libcurl

I am using libcurnet for posting some fields and html or pdf file to server. I post fields but can not upload file to server.

Here is my code :
public static void Main(String[] args)
{ try {
Curl.GlobalInit((int)CURLinitFlag.CURL_GLOBAL_ALL);
FileStream fs = new
FileStream(args[0], FileMode.Open, FileAccess.Read, FileShare.Read);
Easy easy = new Easy();
Easy.ReadFunction rf = new Easy.ReadFunction(OnReadData);
easy.SetOpt(CURLoption.CURLOPT_READFUNCTION,rf);
easy.SetOpt(CURLoption.CURLOPT_UPLOAD, true);
easy.SetOpt(CURLoption.CURLOPT_PUT, true);
easy.SetOpt(CURLoption.CURLOPT_URL, args[1]);
easy.SetOpt(CURLoption.CURLOPT_READDATA, fs);
easy.SetOpt(CURLoption.CURLOPT_INFILESIZE, fs.Length);
Easy.DebugFunction df = new Easy.DebugFunction(OnDebug);
easy.SetOpt(CURLoption.CURLOPT_DEBUGFUNCTION, df);
easy.SetOpt(CURLoption.CURLOPT_VERBOSE, true);
Easy.ProgressFunction pf = new Easy.ProgressFunction(OnProgress);
easy.SetOpt(CURLoption.CURLOPT_PROGRESSFUNCTION, pf);
Easy.WriteFunction wf = new Easy.WriteFunction(OnWriteData);
easy.SetOpt(CURLoption.CURLOPT_WRITEFUNCTION, wf);
easy.SetOpt(CURLoption.CURLOPT_POSTFIELDS, args[2]);
easy.SetOpt(CURLoption.CURLOPT_USERAGENT, "Mozilla 4.0 (compatible; MSIE 6.0; Win32");
easy.SetOpt(CURLoption.CURLOPT_FOLLOWLOCATION, true);
easy.SetOpt(CURLoption.CURLOPT_POST, true);
easy.SetOpt(CURLoption.CURLOPT_VERBOSE, 1);
easy.SetOpt(CURLoption.CURLOPT_STDERR, 0);
easy.Perform();
easy.Cleanup();
fs.Close();
Curl.GlobalCleanup(); } catch (Exception ex) {
Console.WriteLine(ex); } }