3.装饰者模式（Head First 设计模式复习笔记）

public abstract class Beverage
{
    public string description="just beverage without any thing";

    public virtual string GetDescription() {
        return description;
    }

    public abstract double Cost();
}

public abstract class CondimentDecorator:Beverage
{
    public override string GetDescription() {
        return "";
    }
}

public class DarkRoast : Beverage
{
    public DarkRoast()
    {
        description = "DarkRoast";
    }
    public override double Cost()
    {
        return 20;
    }
}

public class Decaf : Beverage
{
    public Decaf()
    {
        description = "Decaf";
    }
    public override double Cost()
    {
        return 40;
    }
}

public class Espresso : Beverage
{
    public Espresso()
    {
        description = "Espresso";
    }
    public override double Cost()
    {
        return 30;
    }
}

public class HouseBlend : Beverage
{
    public  HouseBlend() {
        description = "HouseBlend";
    }
    public override double Cost()
    {
        return 10;
    }
}

public class Mike : CondimentDecorator
{
    public Beverage beverage;
    public Mike(Beverage _beverage) {
        beverage = _beverage;
    }

    public override double Cost()
    {
        return beverage.Cost()+0.1;
    }

    public override string GetDescription()
    {
        return beverage.GetDescription() + ",Mike";
    }
}

public class Mocha : CondimentDecorator
{
    public Beverage beverage;
    public Mocha(Beverage _beverage)
    {
        beverage = _beverage;
    }
        
    public override double Cost()
    {
        return beverage.Cost() + 0.01;
    }

    public override string GetDescription()
    {
        return beverage.GetDescription() + ",Mocha";
    }
}

public class Soy : CondimentDecorator
{
    public Beverage beverage;
    public Soy(Beverage _beverage)
    {
        beverage = _beverage;
    }
        

    public override double Cost()
    {
        return beverage.Cost() + 0.001;
    }

    public override string GetDescription()
    {
        return beverage.GetDescription() + ",Soy";
    }
}

public class Whip : CondimentDecorator
{
    public Beverage beverage;
    public Whip(Beverage _beverage)
    {
        beverage = _beverage;
    }
        

    public override double Cost()
    {
        return beverage.Cost() + 0.0001;
    }

    public override string GetDescription()
    {
        return beverage.GetDescription() + ",Whip";
    }
}

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("顾客：来一杯Houseblend，什么也不加！");
        Beverage b = new HouseBlend();
        Console.WriteLine("这是您点的{0}，一共消费：{1}元", b.GetDescription(), b.Cost());

        Console.WriteLine("顾客：DarkRoast，加Mike和Mocha！");
        Beverage b1 = new DarkRoast();
        b1 = new Mike(b1);
        b1 = new Mocha(b1);
        Console.WriteLine("这是您点的{0}，一共消费：{1}元", b1.GetDescription(), b1.Cost());

        Console.WriteLine("顾客：Espresso，加双份Soy！");
        Beverage b2 = new DarkRoast();
        b2 = new Soy(b2);
        b2 = new Soy(b2);
        Console.WriteLine("这是您点的{0}，一共消费：{1}元", b2.GetDescription(), b2.Cost());

        Console.WriteLine("顾客：来一杯Decaf，加soy,whip,Mike,Mocha！");
        Beverage b3 = new HouseBlend();
        b3 = new Soy(b3);
        b3 = new Whip(b3);
        b3 = new Mike(b3);
        b3 = new Mocha(b3);
        Console.WriteLine("这是您点的{0}，一共消费：{1}元", b3.GetDescription(), b3.Cost());
        Console.ReadKey();
    }
}