Code Contracts were just released under MIT license on GitHub which (I'd think) will probably positively affect their availability https://github.com/CodeContractsDotNet/CodeContracts

Update: On second thought, I think Code Contracts were already available on the free Visual Studio 2013 Community edition: https://visualstudiogallery.msdn.microsoft.com/1ec7db13-3363...

Code Contracts, the library, has always been free. The static checker, the really important piece, was only available in expensive editions for commercial use.

The other problem w/ Code Contracts is inheritance. A call to base.DoStuff(arg); might fail, even though the child class handles it and doesn't need the contract to be satisfied by the parent.

That is not an issue.

Have you read the whole principles behind code contracts?

Derived classes must uphold the same contracts as the base classes, they are only allowed to strengthen them, not to drop conditions.

Is there a difference between design-by-contract and the condition modifications allowed by the Liskov substitution principle? They seem related but I'm not well-enough versed in the differences.

"...the subtype must meet a number of behavioral conditions. These are detailed in a terminology resembling that of design by contract methodology, leading to some restrictions on how contracts can interact with inheritance:

Preconditions cannot be strengthened in a subtype.

Postconditions cannot be weakened in a subtype.

Invariants of the supertype must be preserved in a subtype."

http://en.wikipedia.org/wiki/Liskov_substitution_principle

They are the same.

I was generalizing and though only about pre-conditions.

I see. This is new, it used to be so that although the APIs were available, only Premium, Ultimate and Test had the tooling to generate verifiable builds.