C# Limit creation of class instance to within namespace

Question

I have two objects, RoomManager and Room, there will be several Rooms and one RoomManager. I want the RoomManager to be the only one allowed to create a Room object. So I'm wondering if there is a way to make the Room constructor (and the rest of the Room methods/properties) only accessible to the RoomManager. I was thinking maybe moving them to their own namespace and making Room private or internal or something. From Accessibility Levels (C# Reference) I see that internal is for the entire assembly though, not just the namespace.

Answer 1

No, C# (and .NET in general) has no access modifiers which are specific to namespaces.

One fairly hack solution would be to make Room just have a private constructor, and make RoomManager a nested class (possibly just called Manager):

public class Room
{
    private Room() {}

    public class Manager
    {
        public Room CreateRoom()
        {
            return new Room(); // And do other stuff, presumably
        }
    }
}

Use it like this:

Room.Manager manager = new Room.Manager();
Room room = manager.CreateRoom();

As I say, that's a bit hacky though. You could put Room and RoomManager in their own assembly, of course.

Answer 2

You can do something like this:

var room = Room.Factory.Create();

If the constructor of Room is private, it will still be accessible from Room.Factory if you declare the factory class inside the Room class.

Answer 3

Defining the Room inside of RoomManager itself and making it's constructor private could be helpful.

EDIT : But the best solution I think is that to extract an abstract class of the Room, and expose that class to clients.

No one can create an instance of the abstract class.