Design Pattern Tutorial Part 2: The Decorator Pattern (Structural Pattern) : Example in C#.net

Part 1

Here is an example of the implementation of the Decorator Pattern with C#.net.

   1:      class Program

   2:      {

   3:          static void Main(string[] args)

   4:          {

   5:              IComponent component = new Component();

   6:              Output("Original component: ", component);

   7:              Output("Decorated by A : ", new DecoratorA(component));

   8:              Output("Decorated by B: ", new DecoratorB(component));

   9:              Output("Decorated by A then by B: ", new DecoratorB(new DecoratorA(component)));

  10:              

  11:              DecoratorB b = new DecoratorB(new Component());

  12:              Output("Decorated by B then by A: ", new DecoratorA(b));

  13:              

  14:              // Extended behavior

  15:              Console.WriteLine("\t\t\t\t\t\t" + b.ExtendedBehaviour());

  16:   

  17:              Console.ReadKey();

  18:          }

  19:   

  20:          static void Output(string s, IComponent component)

  21:          {

  22:              Console.WriteLine(s + component.Operation());

  23:          }

  24:      }

  25:   

  26:      public interface IComponent

  27:      {

  28:          string Operation();

  29:      }

  30:   

  31:      public class Component : IComponent

  32:      {

  33:          private string firstName = "Debashish";

  34:          private string lastName = "Shiman";

  35:   

  36:          public string Operation()

  37:          {

  38:              return firstName + " " + lastName;

  39:          }

  40:      }

  41:   

  42:      public class DecoratorA : IComponent

  43:      {

  44:          IComponent component;

  45:   

  46:          public DecoratorA(IComponent c)

  47:          {

  48:              component = c;

  49:          }

  50:   

  51:          public string Operation()

  52:          {

  53:              string s = component.Operation();

  54:              s = "Mr " + s;

  55:              return s;

  56:          }

  57:      }

  58:   

  59:      public class DecoratorB : IComponent

  60:      {

  61:          IComponent component;

  62:   

  63:          public DecoratorB(IComponent c)

  64:          {

  65:              component = c;

  66:          }

  67:   

  68:          public string Operation()

  69:          {

  70:              string s = component.Operation();

  71:              s = s + ", Software Engineer";

  72:              return s;

  73:          }

  74:   

  75:          public string ExtendedBehaviour()

  76:          {

  77:              return " and Web Developer";

  78:          }

  79:      }