public abstract void Visit(ConcreteElementA me);
        public VisitorPattern()
        {
            var concreteElementB = new ConcreteElementB();
            concreteElementB.Accept(new ConcreteVisitor());

            var concreteElementA = new ConcreteElementA();
            concreteElementA.Accept(new ConcreteVisitor());
        }
 public override void Visit(ConcreteElementA me)
 {
     Console.WriteLine("ConcreteElementA");
 }