使用场景：

动态的给一个对象增加一些额外的功能。主体类在多个方向的功能拓展。

实现代码：

// Decorator pattern -- Structural example using System; namespace DoFactory.GangOfFour.Decorator.Structural { /// <summary> /// MainApp startup class for Structural /// Decorator Design Pattern. /// </summary> class MainApp { /// <summary> /// Entry point into console application. /// </summary> static void Main() { // 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(); // Wait for user Console.ReadKey(); } } /// <summary> /// The 'Component' abstract class /// </summary> abstract class Component { public abstract void Operation(); } /// <summary> /// The 'ConcreteComponent' class /// </summary> class ConcreteComponent : Component { public override void Operation() { Console.WriteLine("ConcreteComponent.Operation()"); } } /// <summary> /// The 'Decorator' abstract class /// </summary> abstract class Decorator : Component { protected Component component; public void SetComponent(Component component) { this.component = component; } public override void Operation() { if (component != null) { component.Operation(); } } } /// <summary> /// The 'ConcreteDecoratorA' class /// </summary> class ConcreteDecoratorA : Decorator { public override void Operation() { base.Operation(); Console.WriteLine("ConcreteDecoratorA.Operation()"); } } /// <summary> /// The 'ConcreteDecoratorB' class /// </summary> class ConcreteDecoratorB : Decorator { public override void Operation() { base.Operation(); AddedBehavior(); Console.WriteLine("ConcreteDecoratorB.Operation()"); } void AddedBehavior() { } } }