TimeStampRequestGenerator reqGen = new TimeStampRequestGenerator();            
            TimeStampRequest request = reqGen.Generate(TspAlgorithms.Sha1, new byte[20], BigInteger.ValueOf(100));
            byte[] reqData = request.GetEncoded();
            HttpWebRequest httpReq = (HttpWebRequest)WebRequest.Create("https://tsa.internal....");
            httpReq.Credentials = new NetworkCredential(...);
            httpReq.Method = "POST";
            httpReq.ContentType = "application/timestamp-query";
            httpReq.ContentLength = reqData.Length;

            Stream reqStream = httpReq.GetRequestStream();
            reqStream.Write(reqData, 0, reqData.Length);
            reqStream.Close();
            HttpWebResponse httpResp = (HttpWebResponse)httpReq.GetResponse();

            // Read the response
            Stream respStream = new BufferedStream(httpResp.GetResponseStream()); 
            TimeStampResponse response = new TimeStampResponse(respStream);
            respStream.Close();