/// <summary>
    /// 抓取城市列表
    /// </summary>
    public static void CityCrawler() {
        
        var cityUrl = "http://hotels.ctrip.com/citylist";//定义爬虫入口URL
        var cityList = new List<City>();//定义泛型列表存放城市名称及对应的酒店URL
        var cityCrawler = new SimpleCrawler();//调用刚才写的爬虫程序
        cityCrawler.OnStart += (s, e) =>
        {
            Console.WriteLine("爬虫开始抓取地址：" + e.Uri.ToString());
        };
        cityCrawler.OnError += (s, e) =>
        {
            Console.WriteLine("爬虫抓取出现错误：" + e.Uri.ToString() + "，异常消息：" + e.Exception.Message);
        };
        cityCrawler.OnCompleted += (s, e) =>
        {
            //使用正则表达式清洗网页源代码中的数据
            var links = Regex.Matches(e.PageSource, @"<a[^>]+href=""*(?<href>/hotel/[^>\s]+)""\s*[^>]*>(?<text>(?!.*img).*?)</a>", RegexOptions.IgnoreCase);
            foreach (Match match in links)
            {
                var city = new City
                {
                    CityName = match.Groups["text"].Value,
                    Uri = new Uri("http://hotels.ctrip.com" + match.Groups["href"].Value
                )
                };
                if (!cityList.Contains(city)) cityList.Add(city);//将数据加入到泛型列表
                Console.WriteLine(city.CityName + "|" + city.Uri);//将城市名称及URL显示到控制台
            }
            Console.WriteLine("===============================================");
            Console.WriteLine("爬虫抓取任务完成！合计 " + links.Count + " 个城市。");
            Console.WriteLine("耗时：" + e.Milliseconds + "毫秒");
            Console.WriteLine("线程：" + e.ThreadId);
            Console.WriteLine("地址：" + e.Uri.ToString());
        };
        cityCrawler.Start(new Uri(cityUrl)).Wait();//没被封锁就别使用代理：60.221.50.118:8090
    }