状态模式

 public class Context
    {
        private BaseLight Light = null;

        public Context(BaseLight light)
        {
            Light = light;
        }

        public  void Change()
        {
            Light.Change(this);
        }

        public void Set(BaseLight light)
        {
            Light = light;
          //  Light.Change();
            
        }
    }

    public abstract class BaseLight
    {
        public Light LightState { get; private set; }

        public BaseLight(Light state)
        {
            LightState = state;
        }

        public abstract void Change(Context context);

    }

    public class YellowLight : BaseLight
    {
        public YellowLight() : base(Light.Yellow) { }
        public override void Change(Context context)
        {
            Console.WriteLine("当前灯的颜色是：{0}，Change", this.GetType());
            context.Set(new RedLight());
        }
    }

    public class RedLight : BaseLight
    {
        public RedLight() : base(Light.Red) { }
        public override void Change(Context context)
        {
            Console.WriteLine("当前灯的颜色是：{0}，Change", this.GetType());
            context.Set(new GreenLight());
        }
    }

    public class GreenLight : BaseLight
    {
        public GreenLight() : base(Light.Green) { }
        public override void Change(Context context)
        {
            Console.WriteLine("当前灯的颜色是：{0}，Change", this.GetType());
            context.Set(new YellowLight());
        }
    }

            Context context = new Context(new GreenLight());
            context.Change();
            context.Change();
            context.Change();
            context.Change();
            context.Change();
            context.Change();

            Console.ReadLine();