#region 监视文件夹的变化
            FileSystemWatcher watcher = new FileSystemWatcher();
            watcher.Path = "f:\\";
            watcher.NotifyFilter =//被监控的方面
               NotifyFilters.LastWrite |
               NotifyFilters.FileName |
               NotifyFilters.DirectoryName;

            // 订阅一些事件，当它被触发时（.net(windows)底层触发它，我们不用管），执行我们的方法
            watcher.Changed += (object source, FileSystemEventArgs e) =>
            {
                Console.WriteLine("文件{0}已经被修改,修改类型{1}", e.FullPath, e.ChangeType.ToString());
            };
            watcher.Created += (object source, FileSystemEventArgs e) =>
            {
                Console.WriteLine("文件{0}被建立", e.FullPath);
            };
            watcher.Deleted += (object source, FileSystemEventArgs e) =>
            {
                Console.WriteLine("文件{0}已经被删除", e.FullPath);
            };
            watcher.Renamed += (object source, RenamedEventArgs e) =>
            {
                Console.WriteLine("文件{0}的名称已经从{1}变成了{2}", e.OldFullPath, e.OldName, e.Name);
            };

            // 为true表示开启FileSystemWatcher组件，反之我们的监控将不启作用
            watcher.EnableRaisingEvents = true;
            #endregion

           #region xor两个变量交换
            int a = 2;
            int b = 3;
            Console.WriteLine("a={0}", a);
            Console.WriteLine("b={0}", b);
            a = a ^ b ^ (b = a);
            Console.WriteLine("a={0}", a);
            Console.WriteLine("b={0}", b);
            #endregion