'Security header is not valid' using PayPal sandbox in .NET

Question

I am using the PayPal sandbox in ASP.Net C# 4.0. I added the following web references:

https://www.sandbox.paypal.com/wsdl/PayPalSvc.wsdl
https://www.paypalobjects.com/wsdl/PayPalSvc.wsdl 

When I run this code:

PayPalAPIHelper.PayPalSandboxWS.SetExpressCheckoutReq req = new PayPalAPIHelper.PayPalSandboxWS.SetExpressCheckoutReq()
        {
            SetExpressCheckoutRequest = new PayPalAPIHelper.PayPalSandboxWS.SetExpressCheckoutRequestType()
            {
                Version = Version,
                SetExpressCheckoutRequestDetails = reqDetails
            }
        };

        // query PayPal and get token
        PayPalAPIHelper.PayPalSandboxWS.SetExpressCheckoutResponseType resp = BuildPayPalSandboxWebservice().SetExpressCheckout(req);

In my resp object, the error message says:

Security header is not valid

I was told to give it correct API credentials. I signed up on developer.paypal.com and i'm assuming the email address and password i used are my valid credentials. How and where do I give it my API credentials? Thanks

Answer 1

Did you check the endpoint addresses in your web.config file

Those should be referenced to following url's

For API Certificate => SOAP https://api.sandbox.paypal.com/2.0/

For API Signature => SOAP https://api-3t.sandbox.paypal.com/2.0/

If you are using Signature then use the following code

CustomSecurityHeaderType type = new CustomSecurityHeaderType();
            type.Credentials = new UserIdPasswordType()
            {
                Username = ConfigurationManager.AppSettings["PayPalUserName"], //Not paypal login username
                Password = ConfigurationManager.AppSettings["PayPalPassword"], //not login password
                Signature = ConfigurationManager.AppSettings["PayPalSignature"]
            };

To get Paypal signature follow the link

For more info click here

Update:

Please check the following code it is working for me

CustomSecurityHeaderType type = new CustomSecurityHeaderType();
            type.Credentials = new UserIdPasswordType()
            {
                Username = ConfigurationManager.AppSettings["PayPalUserName"],
                Password = ConfigurationManager.AppSettings["PayPalPassword"],
                Signature = ConfigurationManager.AppSettings["PayPalSignature"]
            };


            PaymentDetailsItemType[] pdItem = new PaymentDetailsItemType[1];
            pdItem[0] = new PaymentDetailsItemType() 
            { 
                Amount = new BasicAmountType(){currencyID = CurrencyCodeType.USD,Value = ItemPrice},
                Name = ItemName,
                Number = ItemNumber,
                Description = ItemDescription, 
                ItemURL = ItemUrl
            };

            SetExpressCheckoutRequestDetailsType sdt = new SetExpressCheckoutRequestDetailsType();
            sdt.NoShipping = "1";
            PaymentDetailsType pdt = new PaymentDetailsType()
            {
                OrderDescription = OrderDesc,
                PaymentDetailsItem = pdItem,
                OrderTotal = new BasicAmountType()
                {                    
                    currencyID = CurrencyCodeType.USD,
                    Value = ItemPrice
                }
            };

            sdt.PaymentDetails = new PaymentDetailsType[] { pdt };
            sdt.CancelURL = "http://localhost:62744/PaymentGateway/PaymentFailure.aspx";
            sdt.ReturnURL = "http://localhost:62744/PaymentGateway/ExpressCheckoutSuccess.aspx";

            SetExpressCheckoutReq req = new SetExpressCheckoutReq()
            {
                SetExpressCheckoutRequest = new SetExpressCheckoutRequestType()
                {
                    SetExpressCheckoutRequestDetails = sdt,
                    Version = "92.0"
                }
            };
            var paypalAAInt = new PayPalAPIAAInterfaceClient();
            var resp = paypalAAInt.SetExpressCheckout(ref type, req);
            if (resp.Errors != null && resp.Errors.Length > 0)
            {
                // errors occured
                throw new Exception("Exception(s) occured when calling PayPal. First exception: " +
                    resp.Errors[0].LongMessage);
            }

            Response.Redirect(string.Format("{0}?cmd=_express-checkout&token={1}",
                ConfigurationManager.AppSettings["PayPalOriginalUrl"], resp.Token));