Microsoft - Domain Oriented N-Layered .NET 4.0 App Sample

Microsoft enters dangerous territory by trying to provide a sample of DDD(Domain Drive Design). It’s very hard to show the benefits of DDD in a simple sample, so I’m really curious how this will work out.

What I noticed immediatelly they start with a long list of things they will NOT try to do:

“This project/sample is willfully restricted to .NET implementation of most used patterns in N-Layered Domain Oriented Architectures based on simple scenarios easy to understand (Customers, Orders, Bank Transfers, etc.). This initiative is NOT trying to teach how to apply DDD. That shouldn't be Microsoft's goal and DDD is much more than Architecture & patterns implementation.
This is an Educational example, not a real world system, it shows educational scenarios, easy to understand useful from a patterns implementation point of view, but not necessarily as a whole business application. The architecture is decoupled and relatively complex so it would allow to grow your system.
Also, this sample goes along with our Architecture Guidance, and there are aspects in the guidance that are not covered by this sample, and viceversa.
Its main goal is to show how to use .NET 4.0 wave technologies implementing typical DDD patterns: N-Layered Architecture, Domain Entities, Aggregates, Repositories, Unit of Work, Domain Services, Application Services, DTOs, DTO-Adapters, etc.”

Although the sample is convoluted, they are still some things you can learn from it(how to NOT do things for example Winking smile ).

What I find even more interesting as a learning experience is how Ayende Rahien jumped on this application and started a review series:

He even took up the challenge and is planning to create his own DDD sample. I’m looking forward to the result…

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A few years ago, I worked as an architect on a big mainframe rewrite. I still count it as one of my failures. Not because the technology was wrong, but because I couldn't convince the management team to simplify the approach. Years later, the organization is still struggling to get the new system up and running. I left the project at the time, because I couldn't put my name behind an approach that would take very long and cost a lot of money without a working system to show for it along the way. Gall’s Law That memory keeps coming back to me, because it's a textbook case of Gall's Law playing out in real life. Gall's Law , from John Gall's Systemantics , states it plainly: A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works, and it cannot be patched to make it work. You have to start over with a simple system that works. What does that mean in practice,...

The art of simplicity

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