Another day, another cool blog post . Design-by-contract is a feature that is built into languages like Eiffel, but is not implemented in the .NET framework. However, there is a third-party library that allows the developer to enforce the design contract in code. Sounds pretty slick. And really, as I see it, this is a best practice, which the library helps simplify. By implementing DBC thoroughly, you force the consumer of a business layer object to enforce the correct values going into the parameters. It does this both before and after executing the "meat" of the code. It can prevent a lot of debugging ugliness around having null reference exceptions popping up hither, thither and yon.