>What is the general method out there in the dotnet world for handling entities and mappers and complex joins or parent-multiple child scenarios later when the product is in maitenance mode?
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>What if Codesmith is used to generate the mappers and business entities? you dont' want to run codesmith every time a new relationship is needed down the road and have to modify that layer.
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>Interested in any ideas and brainstorming anyone is willing to do.

I think most places are rebuilding it. It's a layer that isn't normally directly modified by the devs so it should be safe to do it. It can even be incorporated into the build process so you don't have to think about doing it. I've also seen other products that just require you to update their model of the data when you change the underlying SQL model. It rebuilds whatever it thinks needs rebuilding (in some cases code, other cases it's just meta data).

For my stuff I made a decision to use a methodology where the entities can be rebuilt as the structure changes but I am not using any kind of mapper. I'm perfectly happy using SQL and stored procs, and I wasn't thrilled with most of the syntax that forces an object model on top of SQL. That said, I can see the appeal and I kept looking at various ORM products (NHibernate, LLBLGen, etc.).