Untitled

class RedOrGreenFrobber
{
    private Frobber frobber;
    private RedOrGreenFrobber(Frobber value) {
         this.frobber = value;
    }
    public Value {
         get { return frobber; }
    }
    public static RedOrGreenFrobber RedOrGreen(bool green) { ... } // return a green or red frobber
}
interface Frobber {
    void Frob(Frotz frotz);
}
class RedFrobber implements Frobber { ... }
class GreenFrobber implements Frobber { ... }
public sealed class Frotz
{
    public void Frobbit(RedOrGreenFrobber frobber)
    {
         ...
         frobber.Value.Frob(this);
         ...
    }
}