Promotion exclusion levels in Episerver Commerce

Recently I received a question from a customer regarding combining different discounts. They had an issue that a discount with a bigger discount value was overridden by another discount which was applied with a coupon code. We were trying different combinations to enable such discounts without any luck and then asked Episerver support for help.

The issue

We have item level discounts on two categories where one category has a 30% discount and the second one has a 50% discount. Then we defined an order level discount of 40% when a coupon code is applied. The order of discounts is 50% -> 40% -> 30%.

When we tried to add products from both categories and then apply a coupon code, we got a validation error that it is an invalid discount combination.

The research and the solution

Episerver support sent us a Quicksilver example where this setup worked but with a small difference - 40% discount was an item level discount. We tried to re-create the same setup, but it still did not work.

After some research, I found that Episerver support changed Quicksilver code, which applies discounts. They have changed the exclusion level from Order to Unit when calling ApplyDiscounts on the cart.

cart.ApplyDiscounts(_promotionEngine, new PromotionEngineSettings
    ExclusionLevel = ExclusionLevel.Unit

The default value for ExclusionLevel is Order. So the combination we tried to apply didn't work. Strangely, this is a default value as such discount combinations are common in e-commerce solutions.

So if you need control of combining different discounts on item level, always use ExclusionLevel.Unit.

Thanks to Cuong Phan from Episerver support for help!