Probleme mit Paypal SetExpressCheckout bei der Verwendung von NVP API ASP.net

Hi,
Ich bin der Umsetzung der Integration zwischen meine Facebook-Spiel und Paypal express-Kaufabwicklung-Zahlung-service.

Meiner website entwickelt ASP.net und ich bin mit NVP-API für die integration.

MEIN problem ist, dass ich immer die 10400 Fehler - Um Insgesamt fehlt.

Mein code ist:

//Set the key/value pairs to send in the request
var kvpl = new List<KeyValuePair<string, string>>();
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_PAYMENTACTION", "Sale"));
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_AMT", "23.00"));
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_ITEMAMT", "15.00"));
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_TAXAMT", "5.00"));
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_SHIPPINGAMT", "1.00"));
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_HANDLINGAMT", "1.00"));
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_INSURANCEAMT", "1.00"));
kvpl.Add(new KeyValuePair<string, string>("PAYMENTREQUEST_0_CURRENCYCODE", "ILS"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_NAME0", "The name of product 1"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_NUMBER0", "5543312"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_DESC0", "The description of product 1"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_AMT0", "10.00"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_QTY0", "1"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_NAME1", "The name of product 2"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_NUMBER1", "4431234"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_DESC1", "The description of product 2"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_AMT1", "5.00"));
kvpl.Add(new KeyValuePair<string, string>("L_PAYMENTREQUEST_0_QTY1", "1"));     
kvpl.Add(new KeyValuePair<string, string>("ALLOWNOTE", "1"));
kvpl.Add(new KeyValuePair<string, string>("NOSHIPPING", "1"));

//SetExpressCheckout
bool ret = test.ShortcutExpressCheckout(amt, ref token, ref retMsg, kvpl);

//Check return value
if (ret)
{
    //Success, store the token in the session and redirect to Paypal
    session["token"] = token;
    Response.Redirect( retMsg );
}
else
{
    //Something went wrong
    Response.Redirect("APIError.aspx?" + retMsg);
}

Den code der ShortcutExpressCheckout Methode ist:

public bool ShortcutExpressCheckout(string amt, ref string token, ref string retMsg, List<KeyValuePair<string, string>> customParams)
{
    string host = "www.paypal.com";
    if (bSandbox)
    {
        pendpointurl = "https://api-3t.sandbox.paypal.com/nvp";
        host = "www.sandbox.paypal.com";
    }

    string returnURL = "http://localhost:50020/" + "ConfirmPayment.aspx";
    string cancelURL = "http://localhost:50020/" + "CancelPayment.aspx";

    var encoder = new NVPCodec();
    encoder["VERSION"] = "72.0";
    encoder["METHOD"] = "SetExpressCheckout";        
    encoder["RETURNURL"] = returnURL;
    encoder["CANCELURL"] = cancelURL;

    if (customParams != null)
    {
        customParams.ForEach(kvp => encoder[kvp.Key] = kvp.Value);
    }

    string pStrrequestforNvp = encoder.Encode();
    string pStresponsenvp = HttpCall(pStrrequestforNvp);

    var decoder = new NVPCodec();
    decoder.Decode(pStresponsenvp);

    string strAck = decoder["ACK"].ToLower();
    if (strAck != null && (strAck == "success" || strAck == "successwithwarning"))
    {
        token = decoder["TOKEN"];

        string ECURL = "https://" + host + "/cgi-bin/webscr?cmd=_express-checkout" + "&token=" + token;

        retMsg = ECURL;
        return true;
    }
    else
    {
        retMsg = "ErrorCode=" + decoder["L_ERRORCODE0"] + "&" +
                 "Desc=" + decoder["L_SHORTMESSAGE0"] + "&" +
                 "Desc2=" + decoder["L_LONGMESSAGE0"];

        return false;
    }
}

Den Wunsch erzeugt der code ist:

 METHOD=SetExpressCheckout&
 VERSION=72.0&
 RETURNURL=[removed]&
 CANCELURL=[removed]&
 PAYMENTREQUEST_0_PAYMENTACTION=Sale&
 PAYMENTREQUEST_0_AMT=23.00&
 PAYMENTREQUEST_0_ITEMAMT=15.00&
 PAYMENTREQUEST_0_TAXAMT=5.00&
 PAYMENTREQUEST_0_SHIPPINGAMT=1.00&
 PAYMENTREQUEST_0_HANDLINGAMT=1.00&
 PAYMENTREQUEST_0_INSURANCEAMT=1.00&
 PAYMENTREQUEST_0_CURRENCYCODE=ILS&
 L_PAYMENTREQUEST_0_NAME0=The+name+of+product+1&
 L_PAYMENTREQUEST_0_NUMBER0=5543312&
 L_PAYMENTREQUEST_0_DESC0=The+description+of+product+1&
 L_PAYMENTREQUEST_0_AMT0=10&L_PAYMENTREQUEST_0_QTY0=1&
 L_PAYMENTREQUEST_0_NAME1=The+name+of+product+2&
 L_PAYMENTREQUEST_0_NUMBER1=4431234&
 L_PAYMENTREQUEST_0_DESC1=The+description+of+product+2&
 L_PAYMENTREQUEST_0_AMT1=5.00&
 L_PAYMENTREQUEST_0_QTY1=1.00&
 ALLOWNOTE=1&
 NOSHIPPING=1

Und die Antwort, die ich erhalte ist:

TIMESTAMP=2011%2d09%2d01T12%3a23%3a19Z&
CORRELATIONID=cf89eeaa101ae&
ACK=Failure&
VERSION=2%2e3&
BUILD=2085867&
L_ERRORCODE0=10400&
  L_SHORTMESSAGE0=Transaction%20refused%20because%20of%20an%20invalid%20argument%2e%20See%20additional%20error%20messages%20for%20details%2e&
L_LONGMESSAGE0=Order%20total%20is%20missing%2e&
L_SEVERITYCODE0=Error

Ich überprüfte die Dokumentation, die paypal bietet, und viele Beiträge über dieses Problem, aber ich konnte Sie nicht finden, was mache ich falsch.

Jede Hilfe wird dankbar sein,

Koby