PayPal IPN Integration (Express Checkout - Razor/C#)

我目前正在尝试将PayPal与我的网站集成，并且一切都很顺利-直到我们做IPN检查的那一点。

它直接进入if/elseif/else块，这是它结束的地方。它输出一条消息，内容为:

"无效的状态。form_charset = UTF8 "

这是我的代码。

@using System.Collections.Generic
@using System.Text
@using System.Web
@using System.Web.UI
@using System.Web.UI.HtmlControls
@using System.Web.UI.WebControls
@using System.ComponentModel
@{
    Layout = "~/_SiteLayout.cshtml";
    Page.Title = "Checkout | SSSSS";
    string postUrl = "https://www.paypal.com/cgi-bin/webscr";
    HttpWebRequest req = (HttpWebRequest)WebRequest.Create(postUrl);
    //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 = System.Text.Encoding.UTF8.GetString(param);
    string 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
    StreamWriter streamOut = new StreamWriter(req.GetRequestStream(), 
                             System.Text.Encoding.UTF8);
    streamOut.Write(strRequest);
    streamOut.Close();
    StreamReader streamIn = new StreamReader(req.GetResponse().GetResponseStream());
    string strResponse = streamIn.ReadToEnd();
    streamIn.Close();
    /*/ logging ipn messages... be sure that you give write
    // permission to process executing this code
    string logPathDir = ResolveUrl("Messages");
    string logPath = string.Format("{0}''{1}.txt", 
                     Server.MapPath(logPathDir), DateTime.Now.Ticks);
    File.WriteAllText(logPath, ipnPost);
    /*/
}
@if (strResponse == "VERIFIED")
{
    /*---------------- WILL DO OTHER CHECKS LATER    ------------------*/
    //check the payment_status is Completed
    <p>status is verified</p>
    //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")
{
    //log for manual investigation
    <p>status is invalid.</p>
<p>@ipnPost</p>
}
else
{
    //log response/ipn data for manual investigation
    <p>status is invalid.</p>
<p>@ipnPost</p>
}

我完全不知道为什么这没有像预期的那样工作;我将非常感谢任何帮助。

string strLive = "https://www.paypal.com/cgi-bin/webscr";
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(strLive); 
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;
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();
NameValueCollection ppDetails = HttpUtility.ParseQueryString(strRequest);
if (strResponse == "VERIFIED"){
if (ppDetails["payment_status"] == "Completed"){
//yay, give them goodies
} else if (strResponse == "INVALID"){
//log IP and possibly block them from your web services if malicious
} else {
//log response/ipn data for manual investigation
}
}