I use CartHelper for manage cart. Our system is just haft e-commerce , just can pick products to the cart and send order list by e-mail. It was work fine but today i got an error "Sequence contains more than one matching element" when i try to add product to the cart and retrieve cart. why? How to fix this?
I think you're having same problem with this thread: http://world.episerver.com/Forum/Developer-forum/EPiServer-Commerce/Thread-Container/2014/2/Sequence-contains-more-than-one-matching-element-at-MediachaseCommerceOrdersOrderContextGetCartString-name-Guid-customerId-MarketId-marketId/
I would recommend to update to latest nuget to find out which code unintentionally adds the item to the cart.
Thanks Quan, it's fixed!!!