The best way to assert pre-condition and post-condition of arguments and values in .NET?

Question

I have been thinking about design by contract lately and I was wondering what people think is the best way to assert pre-condition and post-condition of values in .NET? i.e. validating argument values to a method.

Some people recommend Debug.Assert while others talk about using an if statement plus throwing an exception. What are the pros and cons of each?

What frameworks are available that you recommend?

Answer 1

We'll eventually use Code Contracts when .NET 4.0 ships. However, in our production code right now we have had great success with a "Guard" class along with common way to generate exceptions.

For more details, see my post about this.

Answer 2

Another option is Spec#.

Spec# is an extension of the object-oriented language C#. It extends the type system to include non-null types and checked exceptions. It provides method contracts in the form of pre- and postconditions as well as object invariants.