Make object dynamically implement an interface in code

Question

I want to make this test pass - anyone got an idea how to do that?

public class Something
{
    public string Name {get; set}
}

public interface IWithId
{
    public Guid Id {get; set}
}

public class IdExtender 
{
    public static Object Extend(object toExtend)
    {
        ...?
    }
}

public class Tests 
{
    [Test]
    public void Should_extend_any_object()
    {
        var thing = new Something { Name = "Hello World!"};
        var extended = IdExtender.Extend(thing);
        Assert.IsTrue(extended is IWithId);
        Assert.IsTrue(extended.Id is Guid);
        Assert.IsTrue(extened.Name == "Hello World!");
    }
}

I guess something like this could be done with castle dynamic proxy, linfu,etc... but how?

Answer 1

For now I am going with linfu like this:

public class IdExtender 
{
    public static Object Extend(object toExtend)
    {
        var dyn = new DynamicObject(toExtend);
        dyn.MixWith(new WithId {
                                Id = Guid.New()
                               });
        var extended = dyn.CreateDuck<IWithId>(returnValue.GetType().GetInterfaces());
        return extended;
    }
}