Hey,

I am trying to integrate ecommerce to existing site. Only what we need is to sell single product (basically - membership).

I have configured ecommerce module, I was able to display these products on the site.. however - now I need to make order and make direct payment to paypal.
I don't need cart here.
I am using product options for selling to client.
I found one thread about doing direct payment to paypal, but it seems outdated and does not work with kentico 7 (some objects are missing, or methods are different).

So I made custom checkout step.. but when I call

this.ShoppingCartControl.PaymentGatewayProvider.ProcessPayment();

I get an error:

[NullReferenceException: Object reference not set to an instance of an object.]
CMS.Ecommerce.OrderInfoProvider.GetInvoiceNumberInternal(OrderInfo order) +6
CMS.Ecommerce.ShoppingCartInfoProvider.GetShoppingCartResolverData(ShoppingCartInfo cart) +1002
CMS.Ecommerce.ShoppingCartInfoProvider.GetShoppingCartResolverInternal(ShoppingCartInfo cart, Boolean specialMacros) +298
CMS.Ecommerce.PaymentOptionInfoProvider.ResolveUrlMacrosInternal(String url, ShoppingCartInfo cartObj) +117
CMS.EcommerceProvider.CMSPayPalProvider.ProcessPayment() +74
CMSApp.CMSTemplates.Ecommerce.DirectPaypalPayment.Page_Load(Object sender, EventArgs e)

Any ideas on how to implement it correctly?
After successful payment I also want to assign sold membership to user..

any help is appreciated.

regards
Mantas