C# 装饰器模式（Decorator Pattern）

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();  
    }  
}