I’ve been following intently the conversation that has been going around recently surrounding Domain Driven Design and validation within the domain . I have been swirling it around in my head for a bit, and I’m still not quite sure that I am 100% in the game, but I wanted to get my thoughts out on paper (or at least on my blog) so that others would have a chance to respond. In case you have not been following it, the core of the discussion has been revolving around the appropriate place for validation to reside in your application. For many the result was surprising…it should never be in your entities. And interestingly enough, this conclusion seemed to be supported fairly universally by the people responding to this post. Nagging Fears While I guess this should be surprising for me, especially considering the fact that I recently helped design a system where there is a significant amount of validation within entities, I can’t honestly say that it did. The idea of having domain entities validate themselves never really set easy with me. But at the same time, I struggled a bit with the proposed solutions for it. I mean, I can completely understand how contextual validation is, but moving it out of the entities can leave the validation...