using System;

public class Program

{

    public static void Main()

    {

        TheVisitor<object> visitor = new TheVisitor<object>();

        Nodebase nodea = new NodeA();

        Nodebase nodeb = new NodeB();

        visitor.Visit(nodea);

        visitor.Visit(nodeb);

    }

}

​

public abstract class Nodebase { }

public class NodeA : Nodebase { }

public class NodeB : Nodebase { }

​

public abstract class Visitor<T> {

    public abstract T Visit(NodeA node);

    public abstract T Visit(NodeB node);

    public T Visit(Nodebase node)

    {

        Console.WriteLine("Visit(Nodebase)");

        return Visit((dynamic) node);

    }

}

​

public class TheVisitor<T> : Visitor<T> {

    public override T Visit(NodeA node)

    {

        Console.WriteLine("Visit(NodeA)");

        return default(T);

    }

    public override T Visit(NodeB node)

    {

        Console.WriteLine("Visit(NodeB)");

        return default(T);

    }

}