CommerceBuilder API
From AbleCommerce Wiki
The CommerceBuilder API is a set of .NET classes that are used to build the ecommerce store front. They facilitate access to the database, enforcement of business rules and calculations, and order processing.
A compiled compiled help file is available that gives detailed information on the classes and methods available. If you have the Vista operating system, be aware that there is a security feature that may prevent you from opening this file. After downloading, you should go to the file properties and unblock it.