#region 監視文件夾的變化
            FileSystemWatcher watcher = new FileSystemWatcher();
            watcher.Path = "f://";
            watcher.NotifyFilter =//被監控的方面
               NotifyFilters.LastWrite |
               NotifyFilters.FileName |
               NotifyFilters.DirectoryName;

            // 訂閱一些事件，當它被觸發時（.net(windows)底層觸發它，我們不用管），執行我們的方法
            watcher.Changed += (object source, FileSystemEventArgs e) =>
            {
                Console.WriteLine("文件{0}已經被修改,修改類型{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}已經被刪除", e.FullPath);
            };
            watcher.Renamed += (object source, RenamedEventArgs e) =>
            {
                Console.WriteLine("文件{0}的名稱已經從{1}變成了{2}", e.OldFullPath, e.OldName, e.Name);
            };

            // 為true表示開啟FileSystemWatcher組件，反之我們的監控將不啟作用
            watcher.EnableRaisingEvents = true;
            #endregion

#region xor兩個變量交換
            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