装饰模式

    class Program
    ...{
        static void Main(string[] args)
        ...{

            Beverage beverage = new Espresso();
            Console.WriteLine(beverage.getDesciption() + "$" + beverage.cost());

            Beverage beverage2 = new Espresso();
            Beverage beverage3 = new Mocha(beverage2);
            Beverage beverage4 = new Mocha(beverage3);
            beverage3 = new Mocha(beverage2);
            beverage2 = new Mocha(beverage2);
            Console.WriteLine(beverage4.getDesciption() + "$" + beverage4.cost());
        }
    }

    public abstract class Beverage 
    ...{
        public  string description = "Unknown Beverage";

        public String getDesciption() 
        ...{
            return description;
        }
        public abstract double cost();
    }

    public abstract class CondimentDecorator:Beverage
    ...{
        public abstract string getDescription();
    }

    public class Espresso : Beverage 
    ...{
        public Espresso() 
        ...{
            description = "Espresso";
        }
        public override double cost() 
        ...{
            return 1.99;
        }
    }

    public class HouseBlend : Beverage
    ...{
        public HouseBlend()
        ...{
            description = "House Blend Coffee";
        }
        public override double cost() 
        ...{
            return 0.89;
        }
    }

    public class Mocha : CondimentDecorator 
    ...{
        Beverage beverage;
        public Mocha(Beverage beverage) 
        ...{
            this.beverage = beverage;
        }

        public override String  getDescription() 
        ...{
            return beverage.getDesciption() + ",Mocha";
        }

        public override double cost()
        ...{
            return 0.20 + beverage.cost();
        }
    }