Instead of relying on IsValid(xx) calls all over your application, consider taking some advice from Greg Young: Don’t ever let your entities get into an invalid state. What this basically means is that you transition from thinking of entities as pure data containers and more about objects with behaviors. Consider the example of a person’s … Read more
There’s lots of performance advice here, but sadly much of it is guesswork, and little of it points to the real performance considerations. @Holger gets it right by pointing out that we should resist the seemingly overwhelming tendency to let the performance tail wag the API design dog. While there are a zillion considerations that … Read more
Entity Entity means an object that is a single item that the business logic works with, more specifically those which have an identity of some sort. Thus, many people refer to ORM-mapped objects as entities. Some refer to as “entity” to a class an instance of which represents a single row in a database. Some … Read more
Most of the times it is best to place these kind of rules in Specification objects. You can place these Specifications in your domain packages, so anybody using your domain package has access to them. Using a specification, you can bundle your business rules with your entities, without creating difficult-to-read entities with undesired dependencies on … Read more
Define the DTO to the layer where the source of the values comes from. Relative to OP’s question: place the DTO in the Application Service Layer. DTO is an output of that layer, it makes sense if you define it there. Don’t put your DTO in the Domain Layer. The Domain Layer does not care … Read more
It’s ok to store Value Objects in a separate table, for the very reasons you’ve described. However, I think you’re misunderstanding Entities vs VOs – it’s not a persistence related concern. Here’s an example: Assume that a Company and Person both have the same mail Address. Which of these statements do consider valid? “If I … Read more
Just think of it this way, the domain model should be dependent upon nothing and have no infrastructure code within it. The domain model should not be serializable or inherit from some ORM objects or even share them. These are all infrastructure concerns and should be defined separate from the domain model. But, that is … Read more
Collections: It doesn’t matter. There is a distinct difference between collections and references as navigation properties. A reference is an entity. A collections contains entities. This means that initializing a collection is meaningless in terms of business logic: it does not define an association between entities. Setting a reference does. So it’s purely a matter … Read more
Are there any reasons opinion 1) would be preferred to opinion 2) other than speeding up development and reusing code. Option 1 is just because of pure laziness and imagined increased development speed. It’s true that those applications will get version 1.0 built faster. But when those developers reach version 3.0 of the application, they … Read more
If you validate the username using the read model before you send the command, we are talking about a race condition window of a couple of hundred milliseconds where a real race condition can happen, which in my system is not handled. It is just too unlikely to happen compared to the cost of dealing … Read more