What is the best way of using DTOs in a SOA application?

Forget all about the data layer. Create DTO:s that works for each specific web service call.

This would be a mess in large domains and hard to manage and maintain. I really prefer the Nullable DTOs. You should have a single Dto for each object mapped from the real world.

This is the business duty to specify how it should be used. Once you create a Dto, then use it according to you business. Calling GetUserAddress service, and don't expect UserAge or any other thing.

There is a single DTO for Users as we map the user to our Object Oriented User in our design.

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