Question

在.NET体系结构中，有很多设计模式。我想知道观察者模式的含义及其实现方式

Answer 1

Observer模式在C＃中作为事件非常具体化。

Answer 2

维基百科最好地总结了它：

观察者模式（观察者的一个子集）发布/订阅模式）是一个软件设计模式中的一个对象，称为主题，维护他的家属名单，叫做观察者，并通知他们任何状态变化的自动通常通过打电话给他们之一方法。它主要用于实现分布式事件处理系统

观察者（有时称为publish-subscribe模式）最适用于GUI界面，以更新GUI对象的更改状态，例如所有其他对象都可以更新自身（例如，调整窗口大小，然后是所有gui对象，例如按钮可以根据窗口的大小重新对齐。这通常是通过引入EventListeners（这是一个观察者模式）来完成的。

要实现，您可以从以下任一位置查看教程：

MSDN：http://msdn.microsoft.com/en-us/library/ms998543.aspx
维基百科：http://en.wikipedia.org/wiki/Observer_pattern

希望这有帮助。

Answer 3

观察者模式的一个很好的例子显示在MSDN上。

你可以在这里找到它：

http://msdn.microsoft.com/en-us/library/ms998543.aspx

Answer 4

结帐DOFactory。

他们有：

UML图表优点缺点
涉及C＃
实施
样本问题。

Answer 5

这是c＃中观察者模式的一个简单实现，我添加了很多注释，所以希望你能清楚地知道它实际上是什么：）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SimpleObserver
{
    class Program
    {
        static void Main(string[] args)
        {
            Newspaper newspaper = new Newspaper(); //create a Newspaper, which is a realization of Subject
            Grandma grandma = new Grandma(newspaper); //create a new Grandma, which is a realization of Observer
            newspaper.ChangeNews("no news today..."); //when the news get changed, grandma will automatically get it
            newspaper.ChangeNews("still no news..."); //and again
        }
    }

    //the subject which the observers are 'observing'
    //whenever something changes in the subject, the 
    //observers that are registered should be updated
    public interface Subject 
    {
        void RegisterObserver(Observer o); 
        void RemoveObserver(Observer o);
        void NotifyObservers(); 
    }

    //the actual subject, a newspaper which implements
    //the methods declared in the interface and it's own method
    //the goal is that whenever the news property changes 'by 
    //calling ChangeNews(string newNews); all the registered observers will
    //get that new news
    public class Newspaper : Subject
    {
        private List<Observer> observers = new List<Observer>(); //list with observers
        private string news = "initial news, nothing new!"; //the news

        public void RegisterObserver(Observer o)
        {
            this.observers.Add(o);
        }

        public void RemoveObserver(Observer o)
        {
            this.observers.Remove(o);
        }

        public void NotifyObservers()
        {
            foreach (Observer o in this.observers)
                o.Update(news); //update all the observers with the news
        }

        public void ChangeNews(string newNews) //method to manually change the news
        {
            this.news = newNews;
            this.NotifyObservers(); //automatically calls the NotifyObservers() method
        }
    }

    //the actual observer, has a method Update that will be
    //called by the Subject when something changes
    public interface Observer
    {
        void Update(string news);
    }

    //grandma is a observer, whenever the news changes she will be 
    //notified. she also has a reference to the subject instance, so
    //that she can cancel her subscription whenever needed
    public class Grandma : Observer
    {
        private Subject subject;

        public Grandma(Subject subject)
        {
            this.subject = subject; //set reference to the subject
            this.subject.RegisterObserver(this); //register to the subject
        }

        public void Update(string news)
        {
            Console.WriteLine("Granny reads the news, very slowly...");
            Console.WriteLine("The news today is... " + news);
        }
    }

    //possibly other observers go here...
}

我们如何在.NET中实现观察者模式？

5 个答案: