using System;

public class Program

{

    public static void Main()

    {

        var context = new Context();

        context.Handle();

        context.Handle();

    }

}

​

public class Context

{

    public State State{get;set;}

    public Context()

    {

        State = new StateA(this);

    }

    public void Handle()

    {

        State.Handle();

    }

​

}

​

public abstract class State

{

    protected Context Context{get;set;}

    public abstract void Handle();

    protected abstract void ChangeState();

}

​

public class StateA: State

{

    private bool changeState=false;

    public StateA(Context context)

    {

        Context = context;

    }

    public override void Handle()

    {

        Console.WriteLine("This is handle method of StateA.");

        changeState =true;

        ChangeState();

    }

    protected override void ChangeState()

    {

        if(changeState)

        Context.State = new StateB(Context);

    }

}

public class StateB: State

{

 private bool changeState=false;

    public StateB(Context context)

    {

        Context = context;

    }

    public override void Handle()

    {

        Console.WriteLine("This is handle method of StateB.");

        changeState=true;

        ChangeState();

    }

    protected override void ChangeState()

    {

        if(changeState)

        Context.State = new StateA(Context);

    }

}

​

​

​

​

​