装饰器模式动态地给一个对象添加一些额外的职责。就增加功能来说，装饰器模式相比生成子类更为灵活。

// 组件接口  
public interface IComponent  
{  void Operation();  
}  // 具体组件  
public class ConcreteComponent : IComponent  
{  public void Operation()  {  Console.WriteLine("ConcreteComponent.Operation()");  }  
}  // 装饰器抽象类  
public abstract class Decorator : IComponent  
{  protected IComponent _component;  public Decorator(IComponent component)  {  _component = component;  }  public virtual void Operation()  {  _component.Operation();  }  
}  // 具体装饰器  
public class ConcreteDecoratorA : Decorator  
{  public ConcreteDecoratorA(IComponent component) : base(component) {}  public override void Operation()  {  base.Operation();  AddedFunctionality();  }  private void AddedFunctionality()  {  Console.WriteLine("Added functionality in ConcreteDecoratorA");  }  
}  // 客户端代码  
class Program  
{  static void Main(string[] args)  {  IComponent component = new ConcreteComponent();  // 装饰者模式的使用  component = new ConcreteDecoratorA(component);  // 执行操作  component.Operation();  }  
}