Paypal adaptive payment return url is calling twice

I have implemented paypal adaptive payment method and using the web flow.
After making a payment, when i explicitly clicks on return button, the return url calls twice but if i wait for auto redirect then it calls once only.

I am not able to understand why return url is calling twice.

Please advice.

I am using below code.

public static ActionOutput MakeTransactionUsingPaypal(PaymentDetails payment, ShopCart shop_cart)
{
    ReceiverList receiverList = new ReceiverList();
    receiverList.receiver = new List<Receiver>();
    string action_type = "PAY_PRIMARY";
    decimal amnt_to_admin = ((shop_cart.TotalAmountToBePaid * 10) / 100);

    /*Total Amount to Admin Account */
    Receiver rec1 = new Receiver(shop_cart.TotalAmountToBePaid);
    rec1.email = Config.AdminPaypalBusinessAccount;
    rec1.primary = true;

    /*Amount after deducting to Admin Commision to Seller */
    Receiver rec2 = new Receiver(Math.Round((shop_cart.TotalAmountToBePaid - amnt_to_admin), 2, MidpointRounding.ToEven));
    rec2.email = payment.PaypalEmail; // "<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="8beae5fee1d4e6eef9e8e3eae5ffcbf3e2e8e4e6a5e9e2f1">[email protected]</a>";

    receiverList.receiver.Add(rec1);
    receiverList.receiver.Add(rec2);
    PayRequest req = new PayRequest(new RequestEnvelope("en_US"), action_type, Config.PaypalCancelURL, "USD", receiverList, Config.PaypalReturnURL);

    // All set. Fire the request            
    AdaptivePaymentsService service = new AdaptivePaymentsService();

    PayResponse resp = null;
    //TransactionDetail details = new TransactionDetail();

    resp = service.Pay(req);
    String PayKey = resp.payKey;
    String PaymentStatus = resp.paymentExecStatus;
    ResponseEnvelope ResponseEnvelope = resp.responseEnvelope;
    PayErrorList errorList = resp.payErrorList;
    List<ErrorData> errorData = resp.error;
    if (errorData.Count > 0)
    {
        return new ActionOutput
        {
            Status = ActionStatus.Error,
            Message = errorData[0].message
        };
    }
    FundingPlan defaultFundingPlan = resp.defaultFundingPlan;
    WarningDataList warningDataList = resp.warningDataList;
    string redirectUrl = null;
    if (!(resp.responseEnvelope.ack == AckCode.FAILURE) &&
        !(resp.responseEnvelope.ack == AckCode.FAILUREWITHWARNING))
    {
        redirectUrl = ConfigurationManager.AppSettings["PAYPAL_REDIRECT_URL"] + "_ap-payment&paykey=" + resp.payKey;

    }
    return new ActionOutput
    {
        Status = ActionStatus.Successfull,
        Message = "Redirecting to paypal...",
        Results = new List<string> { redirectUrl, resp.payKey }
    };
}

Answers:

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Method 1

@jitendra, I had this same issue and found out that the paypal uses a server side script which redirects the user to the return url after a while and when we explicitly click on return button, then the paypal server script again hits the return url on its own thus we get two responses/hits on our return url.

We can over some this by checking/maintaining the no of responses which we get after the payments are made on paypal.

We can maintain this using cookies on client end or on server using sessions or something else similar.

Hope this helps well.

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