internal static void EventTest()
        {
            Console.WriteLine("事件示例\n");
            NewsPublisher publisher = new NewsPublisher("新闻发布者");

            NewsReader reader1 = new NewsReader("读者1", publisher);
            NewsReader reader2 = new NewsReader("读者2", publisher);
            NewsReader reader3 = new NewsReader("读者3", publisher);

            Console.WriteLine($"{publisher.Name}发布了一则新闻。");
            publisher.PublishNews("早间新闻");

            Console.WriteLine($"{publisher.Name}发布了一则新闻。");
            publisher.PublishNews("晚间新闻");
        }
 //在构造函数中订阅一个事件
 public NewsReader(string name, NewsPublisher publisher)
 {
     Name = name;
     publisher.NewsEvent += HandleNewsEvent;
 }