C#设计模式－装饰者模式（Decorator）

定义

Decorator设计模式动态地将额外的责任附加到对象上。此模式提供了比继承更有弹性的替代方法。

OO设计原则

对扩展开放，对修改关闭。

类图

装饰者模型类图

代码

Component.cs

namespace DesignPattern.Decorator.Structural
{
    public abstract class Component
    {
        public abstract void Operation();
    }
}           

ConcreteComponent.cs

namespace DesignPattern.Decorator.Structural
{
    public class ConcreteComponent : Component
    {
        public override void Operation()
        {
            Console.WriteLine("ConcreteComponent Operation.");
        }
    }
}           

Decorator.cs

namespace DesignPattern.Decorator.Structural
{
    public abstract class Decorator : Component
    {
        protected Component? component;

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

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

ConcreteDecoratorA.cs

namespace DesignPattern.Decorator.Structural
{
    public class ConcreteDecoratorA : Decorator
    {
        public override void Operation()
        {
            base.Operation();
            Console.WriteLine("ConcreteDecoratorA Operation.");
        }
    }
}           

ConcreteDecoratorB.cs

namespace DesignPattern.Decorator.Structural
{
    public class ConcreteDecoratorB : Decorator
    {
        public override void Operation()
        {
            base.Operation();
            Console.WriteLine("ConcreteDecoratorB Operation.");
            AddedBehavior();
        }
        
        private void AddedBehavior()
        {
            Console.WriteLine("ConcreteDecoratorB Added Behavior.");
        }
    }
}           

Program.cs

using DesignPattern.Decorator.Structural;

internal class Program
{
    private static void Main(string[] args)
    {
        ConcreteComponent concreteComponent = new ConcreteComponent();
        ConcreteDecoratorA concreteDecoratorA = new ConcreteDecoratorA();
        ConcreteDecoratorB concreteDecoratorB = new ConcreteDecoratorB();

        concreteDecoratorA.SetComponent(concreteComponent);
        concreteDecoratorB.SetComponent(concreteDecoratorA);

        concreteDecoratorB.Operation();
    }
}