Restrict access to a specific assembly

Question

I'm working on a Winforms project with sql server, splitted in several assemblies.

The first assembly Entities contains DTO like :

public class Attribution
{
    public short UserId { get; set; }
    public User User { get; set; }
}
public class User
{
    public short Id { get; set; }
}

The second assembly Repository is accessing Sql Server database.

The third assembly Service is the link between previous.

There are other layers but this is not the point. I need of course DTO's everywhere in the app.

In sql server, Attribution.UserId and User.Id are the same datas, located in 2 separate tables, linked by Ìnner join.

Attribution.UserId must be public because I need access from Repository,Service, etc... But I don't need it in the "logical" part of the app, what I need is Attribution.User.

At this time I have a UserService class in which there is a GetUser() method and I call this method to get the user in my AttributionService.GetAttribution() method.

Is there a way to restrict access to Attribution.UserId property to Service assembly? Or is it a kind of "good practice violation" to query a User DTO in AttributionService class?

Many thanks for your recommandation.

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Answer 1

One option would be to make the set of the property internal and the use the InternalsVisibleTo attribute to grant access to internals to the Repository assembly.

Another less technical and more logical option would be to make the setter private and let the only way for it to be modified be the classes constructor. That way, your repository can get users built, but nobody can modify the ID later.

As a last option you could create an interface that contains only what the non-repository classes should have access to and pass this around. I'm not a big fan because that means you have to cast it back to your concrete class in the repository and that basically means your repository is lying (saying it accepts an ISomething, but then throwing if the ISomething is not the exact, concrete Something it expects).