Hi Sibren,

Ok, well firstly, you probably shouldn't finalize the order at this point. You really should only call this once you have some kind of notification from payment gateway as once an order is finalized, there is no going back.

In terms of generating the HTML form to render, unfortunately we only currently have one way of doing this, which is by using the @Html.BeginPaymentForm helper which runs in a razor file.

You might be able to get the payment providers form definition by calling the paymentProvider.GenerateForm method, but you'd be responsible for converting that into an actual form.

To do this, you'd probably need to do something like

var paymentMethod = paymentMethodService.GetPaymentMethod(writableOrder.PaymentInfo.PaymentMethodId.Value);
var paymentProvider = paymentProviderService.GetPaymentProvider(paymentMethod.PaymentProviderAlias);
var settings = new ReadOnlyDictionary(translationService.TranslateValues(paymentMethod.PaymentProviderSettings, writableOrder.LanguageIsoCode));

var continueUrl = uriResolver.GetContinueUrl(paymentMethod.PaymentProviderAlias, orderReference, hashProvider);
var cancelUrl = uriResolver.GetCancelUrl(paymentMethod.PaymentProviderAlias, orderReference, hashProvider);
var callbackUrl = uriResolver.GetCallbackUrl(paymentMethod.PaymentProviderAlias, orderReference, hashProvider);

var formResult = paymentProvider.GenerateForm(writableOrder, continueUrl, cancelUrl, callbackUrl, settings);

This is ultimately what the Html.BeginPaymentForm helper does and then renders an MvcForm based on the formResult settings.

A few things to note though.

1) The Html.BeginPaymentForm method is generally also responsible for ensuring at the last minute that if there is a logged in member, that their member ID is assigned to the order. If you need this behavior, you'll have to implement this too.

2) The formResult object can also contain a MetaData property which it is expected that whatever is in this, is copied over to the order's properties collection so again you'll need to do this. This can be essential if the payment provider stores values in the order that it expects when it comes to finalize the order later.

You'r implementation for this should be something like

if (formResult.MetaData != null && formResult.MetaData.Count > 0)
{
    writableOrder.SetProperties(formResult.MetaData
        .ToDictionary(x => x.Key, x => new PropertyValue(x.Value, true, false)), SetBehavior.Merge);
}

As such, you may want to move your _vendrApi.SaveOrder(order); and uow.Compelte() to run AFTER this update.

We do need to make all this a bit nicer / easier for SPA usage but I need to put some time aside with some devs to discuss what this API would look like.

In the meantime you'll either need to do the above, or, look at doing something where you ajax load in a razor partial that actually calls Html.BeginPaymentForm.

Hope this helps

Matt