Decorator Design Pattern - C#

Attaching additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.

The classes and objects participating in this pattern are:

• Component 
  • defines the interface for objects that can have responsibilities added to them dynamically.
• ConcreteComponent   
  • defines an object to which additional responsibilities can be attached.
• Decorator 
  • maintains a reference to a Component object and defines an interface that conforms to Component's interface.
• ConcreteDecorator 
  • adds responsibilities to the component.

Code :-

//Component
namespace DecoratorDemo.Component
{
    public interface IHome
    {
        string Make { get; }
        double GetPrice();
    }
}


//Concrete Component

  public class MyHome : Component.IHome
    {
        public string Make {
            get
            {
                return "MyHome";
            }
        }

        public double GetPrice()
        {
            return 8000000;
        }
    }


//Decorator
 public abstract class HomeDecorator : IHome
    {
        private readonly IHome home;

        public HomeDecorator(IHome home)
        {
            this.home = home;
        }
        public string Make
        {
            get
            {
                return "MyHome";
            }
        }

        public double GetPrice()
        {
            return home.GetPrice();
        }
        public abstract double GetDiscountPrice();
    }

  // Concrete Decorator
  public class OfferPrice : HomeDecorator
    {
        public OfferPrice(IHome home)  : base(home)
        {

        }
        public override double GetDiscountPrice()
        {
            return .8 * base.GetPrice();   
        }
    }

// Execution

 class Program
    {
        static void Main(string[] args)
        {
            IHome home = new MyHome();
            HomeDecorator decorator = new OfferPrice(home);

            Console.WriteLine(string.Format("Make : {0} Price {1} DiscountPrice {2}", decorator.Make, decorator.GetPrice(), decorator.GetDiscountPrice()));
        }
    }


OutPut
Make : MyHome Price 8000000 DiscountPrice 6400000