C# FileSystemWatcher 组件应用

    在ScheduledJob专案中，要用到很多自定义的DLL组件，为了保证运行的效能，我们采用“缓存”的方式对这些组件进行事先加载，待应用时在内存中既可找到对应的组件并运行，而无需每次都Load. 而这些组件随时都可能有异动，可能新增，可能修改，此时要保证缓存的内容也及时更新，就必须采取一种机制保证，这些组件表更时，能同时更新到内存缓存中。

    在C#中我们可以采用FileSystemWatcher组件实现。

using System;

using System.Collections.Generic;

using System.IO;



namespace fileSystemWatcherDemo

{

    /// <summary>

    /// FileSystemWatcher 组件应用Demo 1

    /// </summary>

    class fileSystemWatcherDemo

    {

        private FileSystemWatcher dllWatcher;



        static void Main(string[] args)

        {

            Console.WriteLine("file Watcher Started  at " + DateTime.Now.ToString());



            fileSystemWatcherDemo watcher = new fileSystemWatcherDemo();

            watcher.beginWatcher();



            Console.Read();

        }



        private void beginWatcher()

        {

            dllWatcher = new FileSystemWatcher();

            dllWatcher.Path = @"D:\ScheduledJob\DLL";

            dllWatcher.IncludeSubdirectories = false;

            dllWatcher.Filter = "*.*";

            dllWatcher.NotifyFilter = NotifyFilters.LastWrite;

            dllWatcher.EnableRaisingEvents = true;

            dllWatcher.Changed += new FileSystemEventHandler(dllWatcher_Changed);

        }



        void dllWatcher_Changed(object sender, FileSystemEventArgs e)

        {

            try

            {

                Console.WriteLine("file" + e.FullPath + "was updated at " + DateTime.Now.ToString());

            }

            catch (Exception ex)

            {

                Console.WriteLine("file" + e.FullPath + "can't be updated at " + DateTime.Now.ToString() + ex.Message);

            }

        }

    }

}

测试下：运行后，在DLL文件夹中丢一个123.txt,出现如下结果：

   

发现一个问题，丢一个文件进去，OnChange事件触发了多次（这里是两次），一个文件也被解析执行了多次。

    目前这种情况还没有找到彻底解决的办法，而为了保证一次异动，changed事件只触发一次，只能采取一些不是办法的办法来避免。根据这些多次触发的事件是在短时间内完成的特点，这里采用一个键值对，键（文件名称）值（档次执行的时间点）对来记录一个文件异动的时间，当再次触发时，检查这个键值对，找到对应的文件，看它上次执行的时间，如果在设置的特定的时间内，则返回，取消本次执行。

using System;

using System.Collections.Generic;

using System.IO;



namespace fileSystemWatcherDemo

{

    /// <summary>

    /// FileSystemWatcher 组é件t应|用?Demo

    /// </summary>

    class fileSystemWatcherDemo

    {

        private FileSystemWatcher dllWatcher;



        //用于解决同一文件一次异动的多次事件触发问ê题a

        private Dictionary<string, DateTime> watcherChangedTimes = null;



        static void Main(string[] args)

        {

            Console.WriteLine("file Watcher Started  at " + DateTime.Now.ToString());



            fileSystemWatcherDemo watcher = new fileSystemWatcherDemo();

            watcher.beginWatcher();



            Console.Read();

        }



        private void beginWatcher()

        {

            watcherChangedTimes = new Dictionary<string, DateTime>();



            dllWatcher = new FileSystemWatcher();

            dllWatcher.Path = @"D:\ScheduledJob\DLL";

            dllWatcher.IncludeSubdirectories = false;

            dllWatcher.Filter = "*.*";

            dllWatcher.NotifyFilter = NotifyFilters.LastWrite;

            dllWatcher.EnableRaisingEvents = true;

            dllWatcher.Changed += new FileSystemEventHandler(dllWatcher_Changed);



        }



        void dllWatcher_Changed(object sender, FileSystemEventArgs e)

        {

            #region 60秒内同一个文件只处理一次
             DateTime now = DateTime.Now;

            int reloadSeconds = 60;

            if (watcherChangedTimes.ContainsKey(e.FullPath))

            {

                if (now.Subtract(watcherChangedTimes[e.FullPath]).TotalSeconds < reloadSeconds)

                {

                    return;

                }

                else

                {

                    watcherChangedTimes[e.FullPath] = now;

                }

            }

            else

            {

                watcherChangedTimes.Add(e.FullPath, now);

            }

            #endregion



            try

            {

               Console.WriteLine("file" + e.FullPath + "was updated at " + DateTime.Now.ToString());

            }

            catch (Exception ex)

            {

                Console.WriteLine("file" + e.FullPath + "can't be updated at " + DateTime.Now.ToString() + ex.Message);

            }

        }

    }

}

再丢一个文件1.jpg进去，运行结果如下：