Paypal IPN integration issues

Question

I am trying to process the response from paypal on my page. I found this code from paypal documentation itself. When the response is valid, some parameters needs to be processed like txn_id and payment_completed. How should i do that?? the code is as follows

string strSandbox = "https://www.sandbox.paypal.com/cgi-bin/webscr";
        // string strLive = "https://www.paypal.com/cgi-bin/webscr";
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(strSandbox);

        //Set values for the request back
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
        byte[] param = Request.BinaryRead(HttpContext.Current.Request.ContentLength);
        string strRequest = Encoding.ASCII.GetString(param);
        strRequest += "&cmd=_notify-validate";
        req.ContentLength = strRequest.Length;

        //for proxy
        //WebProxy proxy = new WebProxy(new Uri("http://url:port#"));
        //req.Proxy = proxy;

        //Send the request to PayPal and get the response
        StreamWriter streamOut = new StreamWriter(req.GetRequestStream(), System.Text.Encoding.ASCII);
        streamOut.Write(strRequest);
        streamOut.Close();
        StreamReader streamIn = new StreamReader(req.GetResponse().GetResponseStream());
        string strResponse = streamIn.ReadToEnd();
        streamIn.Close();

        if (strResponse == "VERIFIED")
        {

            //UPDATE YOUR DATABASE

            //TextWriter txWriter = new StreamWriter(Server.MapPath("../uploads/") + Session["orderID"].ToString() + ".txt");
            //txWriter.WriteLine(strResponse);
            //txWriter.Close();

            //check the payment_status is Completed
            //check that txn_id has not been previously processed
            //check that receiver_email is your Primary PayPal email
            //check that payment_amount/payment_currency are correct
            //process payment
        }
        else if (strResponse == "INVALID")
        {
            //UPDATE YOUR DATABASE

            //TextWriter txWriter = new StreamWriter(Server.MapPath("../uploads/") + Session["orderID"].ToString() + ".txt");
            //txWriter.WriteLine(strResponse);
            ////log for manual investigation
            //txWriter.Close();
        }
        else
        {  //UPDATE YOUR DATABASE

            //TextWriter txWriter = new StreamWriter(Server.MapPath("../uploads/") + Session["orderID"].ToString() + ".txt");
            //txWriter.WriteLine("Invalid");
            ////log response/ipn data for manual investigation
            //txWriter.Close();
        }
    }

Give me some inputs please. Thanks

Answer 1

After you get the response and you know that is valid, the parameters have been posted to you and you can get them using the .Form For example:

if (strResponse == "VERIFIED")
{
    // Now All informations are on
    HttpContext.Current.Request.Form;
    // for example you get the invoice like this
    HttpContext.Current.Request.Form["invoice"] 
    // or the payment_status like
    HttpContext.Current.Request.Form["payment_status"] 
}
else
{
  //log for manual investigation
}