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How do you implement the "Last 20 something" property in your domain class?

Let's say I need to implement a domain model for StackOverflow.

If I am doing an ORM, how can I define a property (and a map) to get "recent comments" and other "recent" things? It seems to me that this should be reflected in the domain model.

Sometimes I may need "all comments" though ...

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I can be affected by the ORM tool, but I am treating this as a request, not a domain property. The domain contains associations and the repository encapsulates requests such as the one you describe.



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You would query your repository for the latest comments from a specific user. something like

IList<Comment> recentComments = repository.GetRecentComments(user,20);

YOU CAN do this in a model, but depending on how many comments you expect, I would avoid it. The model doesn't need to know how to populate itself, that is, how the repository works; however, if you use something like NHibernate it will be there.



public class User{

 public IList<Comment> Comments { get;set;}

 public IList<Comment> GetRecentComments()
 {
   // Logic
 }


}

In this implementation, you will always download ALL comments to get the last 20. Not a big deal if there are only 50 comments, but if there are 5000 comments, you have quite a lot of overhead.

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