protected void Page_Load(object sender, EventArgs e)

        {

            string strFormValues;

            string strNewValue;

            string strResponse;

            string reqUrl = "https://www.sandbox.paypal.com/cgi-bin/webscr";

            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(reqUrl);

            //设置request属性

            req.Method = "POST";

            req.ContentType = "application/x-www-form-urlencoded";

            byte[] param = HttpContext.Current.Request.BinaryRead(HttpContext.Current.Request.ContentLength);

            strFormValues = Encoding.ASCII.GetString(param);

            //建议在此将接收到的信息记录到日志文件中以确认是否收到IPN信息

            strNewValue = strFormValues + "&cmd=_notify-validate";

            req.ContentLength = strNewValue.Length;

            //发送request

            StreamWriter stOut = new StreamWriter(req.GetRequestStream(), Encoding.ASCII);

            stOut.Write(strNewValue);

            stOut.Close();



            //回复IPN并接受反馈信息

            StreamReader stIn = new StreamReader(req.GetResponse().GetResponseStream());

            strResponse = stIn.ReadToEnd();

            stIn.Close();            



            //确认IPN是否合法

            if (strResponse == "VERIFIED")