gistfile1.txt

class DecoratorPattern
{
    interface IComponent
    {
        string Operation();
    }

    class Component : IComponent
    {
        public string Operation()
        {
            return "I am walking ";
        }
    }


    class DecoratorA : IComponent
    {
        private IComponent component;

        public DecoratorA(IComponent component)
        {
            this.component = component;
        }

        public string Operation()
        {
            string s = component.Operation();
            s += "and listening to Classic FM ";
            return s;
        }
    }

    class DecoratorB : IComponent
    {
        private IComponent component;

        public string AddedState
        {
            get
            {
                return "past the Coffee Shop ";
            }
        }

        public DecoratorB(IComponent component)
        {
            this.component = component;
        }

        public string Operation()
        {
            string s = component.Operation();
            s += "to school ";
            return s;
        }

        public string AddedBehaviour()
        {
            return "and I bought a cappuccino ";
        }
    }

    static class Client
    {
        static void Display(string s, IComponent component)
        {
            Console.WriteLine(s + component.Operation());
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Decorator Pattern\n");

            IComponent component = new Component();
            Display("1. Basic Component: " , component);
            
            DecoratorA decoratorA = new DecoratorA(component);
            Display("2. A-decorated: ", decoratorA);

            DecoratorB decoratorB = new DecoratorB(component);
            Display("3. B-decorated: ", decoratorB);

            DecoratorB decoratorBA = new DecoratorB(new DecoratorA(component));
            Display("4. B-A-decorated: ", decoratorBA);

            DecoratorA decoratorAB = new DecoratorA(new DecoratorB(component));
            Display("4. A-B-decorated: ", decoratorAB);

            Console.WriteLine("\t\t\t" + decoratorB.AddedState + decoratorB.AddedBehaviour());
        }
    }