using System;

using System.Collections.Generic;

​

public interface IOperation

{

    void Apply(HeadingNode node);

    void Apply(AnchorNode node);

}

​

public class HighlightOperation: IOperation

{

    public void Apply(HeadingNode node)

    {

        Console.WriteLine("Higlighting heading");

    }

    public void Apply(AnchorNode node)

    {

        Console.WriteLine("Higlighting anchor");

    }

}

​

public class PlainTextOperation: IOperation

{

    public void Apply(HeadingNode node)

    {

        Console.WriteLine("PlainText heading");

    }

    public void Apply(AnchorNode node)

    {

        Console.WriteLine("PlainText anchor");

    }

}

​

public interface IHtmlNode

{

    void Execute(IOperation operation);

}

​

public class HeadingNode: IHtmlNode

{

    public void Execute(IOperation operation)

    {

        operation.Apply(this);

    }

}

public class AnchorNode: IHtmlNode

{

    public void Execute(IOperation operation)

    {

        operation.Apply(this);

    }

}

​

public class HtmlDocument

{

    private List<IHtmlNode> nodes = new List<IHtmlNode>();

    public void Add(IHtmlNode node)

    {

        nodes.Add(node);

    }

    public void Execute(IOperation operation) {

        foreach(var node in nodes)

        {

            node.Execute(operation);

        }

    }

}

public class Program

{

    public static void Main()

    {

        var htmlDocument = new HtmlDocument();

        htmlDocument.Add(new HeadingNode());

        htmlDocument.Add(new AnchorNode());

        htmlDocument.Execute(new HighlightOperation());

        htmlDocument.Execute(new PlainTextOperation());

    }

}