装饰模式

    // Decorator pattern -- Structural example  
    using System;
   

    // "Component"
    abstract class Component
    {
      // Methods
      abstract public void Operation();
   }
  

   // "ConcreteComponent"
   class ConcreteComponent : Component
   {
     // Methods
     override public void Operation()
     {
       Console.WriteLine("ConcreteComponent.Operation()");
     }
   }
  

   // "Decorator"
   abstract class Decorator : Component
   {
     // Fields
     protected Component component;
  

     // Methods
     public void SetComponent( Component component )
     {
       this.component = component;
     }
  

     override public void Operation()
     {
       if( component != null )
         component.Operation();
     }
   }
  

   // "ConcreteDecoratorA"
   class ConcreteDecoratorA : Decorator
   {
     // Fields
     private string addedState;
 
    // Methods
     override public void Operation()
     {
       base.Operation();
       addedState = "new state";
       Console.WriteLine("ConcreteDecoratorA.Operation()");
     }
   }
  
   // "ConcreteDecoratorB"
   class ConcreteDecoratorB : Decorator
   {
     // Methods
     override public void Operation()
     {
       base.Operation();
       AddedBehavior();
       Console.WriteLine("ConcreteDecoratorB.Operation()");
     }
  

     void AddedBehavior()
     {
     }
   }
  
   /**//// <summary>
   /// Client test
   /// </summary>
   public class Client
   {
     public static void Main( string[] args )
     {
       // Create ConcreteComponent and two Decorators
       ConcreteComponent c = new ConcreteComponent();
       ConcreteDecoratorA d1 = new ConcreteDecoratorA();
       ConcreteDecoratorB d2 = new ConcreteDecoratorB();
 
       // Link decorators
       d1.SetComponent( c );
       d2.SetComponent( d1 );
        
       d2.Operation();
       Console.ReadLine();
    }
}