void Main(){    (new Director()).Show(new VisitorA());}class Director{    List<Element> elements = new List<Element>{        new ElementA(),        new ElementB()    };    public void Show(Visitor v){        foreach (var element in elements)        {            element.Show(v);        }    }}abstract class Element{    public abstract void Show(Visitor v);}class ElementA:Element{    public override void Show(Visitor v){ v.ByEleA(this); }}class ElementB:Element{    public override void Show(Visitor v){ v.ByEleB(this); }}abstract class Visitor{    public abstract void ByEleA(ElementA ea);    public abstract void ByEleB(ElementB eb);}class VisitorA:Visitor{    public override void ByEleA(ElementA ea){        "EA meet VA".Dump();    }    public override void ByEleB(ElementB eb){        "EB meet VA".Dump();    }}class VisitorB:Visitor{    public override void ByEleA(ElementA ea){        "EA meet VB".Dump();    }    public override void ByEleB(ElementB eb){        "EB meet VB".Dump();    }}