using System;

public class Program

{

    public static void Main()

    {

        IToturial nowStep = new Toturial1();

        nowStep.Run(2);

    }

}

​

public interface IToturial

{

    void Run(int step);

}

​

public class Toturial1 : IToturial

{

    IToturial nextStep;

    public Toturial1()

    {

        nextStep = new Toturial2();

    }

    public void Run(int step)

    {

        if (step <= 1)

            RunTutorial();

        else

            nextStep.Run(step);

    }

    public void RunTutorial()

    {

        Console.WriteLine("step 1");

    }

}

​

public class Toturial2 : IToturial

{

    IToturial nextStep;

    public Toturial2()

    {

        nextStep = new Toturial3();

    }

    public void Run(int step)

    {

        if (step <= 2)

            RunTutorial();

        else

            nextStep.Run(step);

    }

    public void RunTutorial()

    {

        Console.WriteLine("step 2");

    }

}

​

public class Toturial3 : IToturial

{

    IToturial nextStep;

    public Toturial3()

    {

    }

    public void Run(int step)

    {

        RunTutorial();

    }

    public void RunTutorial()

    {   

        Console.WriteLine("step 3");

    }

}