Enforcement of returning non-null

Question

We are implementing some web services, and need to ensure that some of our methods always return non-null values.

We've investigated two ways of doing this:

• Using code contracts, and returning the default value using Ensures constraints on the return value.
• Using an aspect-oriented programming approach using PostSharp.

Both approaches work, but I'm wondering whether there are any other approaches that we should consider.

How would you enforce non-null return values?

---

Looks like there was a similar question on SO, and Jon Skeet recommends the Code Contract approach.