因此，我阅读了 IPN 文档，并且阅读了我找到的大量示例。我尝试了几种不同的解决方案，但在它们不起作用后，我只是简单地复制并粘贴了 PayPal IPN 页面上记录的内容。因此，它仍然无法正常工作。我的 IPN 历史显示它正在继续重新发送消息。下面的代码 - 缺少什么？
protected void Page_Load(object sender, EventArgs e)
{
const string postUrl = "https://www.paypal.com/cgi-bin/webscr";
var req = (HttpWebRequest)WebRequest.Create(postUrl);
//Set values for the request back
req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";
var param = Request.BinaryRead(HttpContext.Current.Request.ContentLength);
var strRequest = Encoding.ASCII.GetString(param);
var ipnPost = strRequest;
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
var streamOut = new StreamWriter(req.GetRequestStream(), Encoding.ASCII);
streamOut.Write(strRequest);
streamOut.Close();
// ReSharper disable AssignNullToNotNullAttribute
var streamIn = new StreamReader(req.GetResponse().GetResponseStream());
// ReSharper restore AssignNullToNotNullAttribute
var strResponse = streamIn.ReadToEnd();
streamIn.Close();
// logging ipn messages... be sure that you give write
// permission to process executing this code
//
if (strResponse == "VERIFIED")
{
//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
var mailer = new Emailer();
mailer.SendMail("from@domain.com", "to@domain.com", "Thank you!",
"Thank you for your sponsorship. Good luck on your results!<br /><br />" + ipnPost);
}
else if (strResponse == "INVALID")
{
//log for manual investigation
}
}