using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var monkey = new MonkeyHandler();

        var squirrel = new SquirrelHandler();

        var dog = new DogHandler();

        monkey.SetNext(squirrel).SetNext(dog);

        Console.WriteLine("Chain: Monkey > Squirrel > Dog\n");

        Client.ClientCode(monkey);

        Console.WriteLine();

​

        Console.WriteLine("Subchain: Squirrel > Dog\n");

        Client.ClientCode(squirrel);

    }

}

​

public class Client

{

    public static void ClientCode(AbstractHandler handler)

    {

        foreach(var food in new List<string> {"Nut", "Banana", "MeatBall"})

        {

            Console.WriteLine($"Client: Who wants a {food}");

            var result = handler.Handle(food);

            if(result != null)

            {

                Console.WriteLine($"{result}");

            }

            else

            {

                Console.WriteLine($"{food} was left un touched.");

            }

        }

    }

}

​

public interface IHandler

{

    IHandler SetNext(IHandler handler);

    object  Handle(object request);

}

​

public abstract class AbstractHandler : IHandler

{

    private IHandler _nextHandler;

    public IHandler SetNext(IHandler handler)

    {

        this._nextHandler = handler;

        return handler;

    }

    public virtual object Handle(object request)

    {

        if(this._nextHandler != null)

        {

            return this._nextHandler.Handle(request);

        }

        else

        {

            return null;

        }

    }

}

​

public class MonkeyHandler : AbstractHandler

{

    public override object Handle(object request)

    {

        if((request as string) == "Banana")

        {

            return $"Monkey eat: {request.ToString()}";

        }

        else

        {

            return base.Handle(request);

        }

    }

}

​

public class SquirrelHandler : AbstractHandler

{

    public override object Handle(object request)

    {

        if((request as string) == "Nut")

        {

            return $"Squirrel eat: {request.ToString()}";

        }

        else

        {

            return base.Handle(request);

        }

    }

}

​

public class DogHandler : AbstractHandler

{

    public override object Handle(object request)

    {

        if((request as string) == "MeatBall")

        {

            return $"Dog eat: {request.ToString()}";

        }

        else

        {

            return base.Handle(request);

        }

    }

}