using System;

​

public abstract class State

{

    public abstract string Name{get;}

    public abstract void Handle(Context context);

}

​

public class Context

{

    private State state;

    public Context()

    {

    }

    public void SetState(State state)

    {

        this.state =  state;

        Console.WriteLine("The current state {0} \n", state.Name);

    }

    public void Request()

    {

        this.state.Handle(this);

    }

}

​

public class ConcreteStateA : State

{

    public override string Name {get{return "ConcreteStateA";}}

    public override void Handle(Context context)

    {

        Console.WriteLine("{0} - is handle here", this.Name);

        context.SetState(new ConcreteStateB());

    }

}

​

public class ConcreteStateB : State

{

    public override string Name {get{return "ConcreteStateB";}}

    public override void Handle(Context context)

    {

        Console.WriteLine("{0} - is handle here", this.Name);

        context.SetState(new ConcreteStateA());

    }

}

public class Program

{

    public static void Main()

    {

        var ctx = new Context();

        ctx.SetState(new ConcreteStateB());

        ctx.Request();

        Console.WriteLine("\n");

        ctx.Request();

    }

}