C# MongoDB: How to correctly map a domain object?

It is possible to serialize/deserialize classes where the properties are read-only. If you are trying to keep your domain objects persistance ignorant, you won’t want to use BsonAttributes to guide the serialization, and as you pointed out AutoMapping requires read/write properties, so you would have to register the class maps yourself. For example, the class:

public class C {
    private ObjectId id;
    private int x;

    public C(ObjectId id, int x) {
        this.id = id;
        this.x = x;
    }

    public ObjectId Id { get { return id; } }
    public int X { get { return x; } }
}

Can be mapped using the following initialization code:

BsonClassMap.RegisterClassMap<C>(cm => {
    cm.MapIdField("id");
    cm.MapField("x");
});

Note that the private fields cannot be readonly. Note also that deserialization bypasses your constructor and directly initializes the private fields (.NET serialization works this way also).

Here’s a full sample program that tests this:

http://www.pastie.org/1822994