使用延迟的FileSystemWatcher来避免重复触发事件

问题：

　　程序里需要监视某个目录下的文件变化情况: 一旦目录中出现新文件或者旧的文件被覆盖，程序需要读取文件内容并进行处理；但在实际处理中发现当一个文件产生变化时，Change事件被反复触发了好几次。这样可能的结果是造成同一文件的重复处理。
解决方法：

　　针对上面的问题，于是写了一个可以延迟FileSystemWatcher发出的事件的Class DelayFileSystemWatcher。

using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;

namespace Utility
{
    public class DelayFileSystemWatcher
    {
        private readonly Timer m_Timer;
        private readonly Int32 m_TimerInterval;
        private readonly FileSystemWatcher m_FileSystemWatcher;
        private readonly FileSystemEventHandler m_FileSystemEventHandler;
        private readonly Dictionary<String, FileSystemEventArgs> m_ChangedFiles = new Dictionary<string, FileSystemEventArgs>();

        public DelayFileSystemWatcher(string path, string filter, FileSystemEventHandler watchHandler, int timerInterval)
        {
            m_Timer = new Timer(OnTimer, null, Timeout.Infinite, Timeout.Infinite);
            m_FileSystemWatcher = new FileSystemWatcher(path, filter);
            m_FileSystemWatcher.NotifyFilter = NotifyFilters.FileName | NotifyFilters.LastWrite | NotifyFilters.CreationTime;
            m_FileSystemWatcher.Created += fileSystemWatcher_Changed;
            m_FileSystemWatcher.Changed += fileSystemWatcher_Changed;
            m_FileSystemWatcher.Deleted += fileSystemWatcher_Changed;
            m_FileSystemWatcher.Renamed += fileSystemWatcher_Changed;
            m_FileSystemWatcher.EnableRaisingEvents = true;
            m_FileSystemEventHandler = watchHandler;
            m_TimerInterval = timerInterval;
        }

        public void fileSystemWatcher_Changed(object sender, FileSystemEventArgs e)
        {
            lock (m_ChangedFiles)
            {
                if (!m_ChangedFiles.ContainsKey(e.Name))
                {
                    m_ChangedFiles.Add(e.Name, e);
                }
            }
            m_Timer.Change(m_TimerInterval, Timeout.Infinite);
        }

        private void OnTimer(object state)
        {
            Dictionary<String, FileSystemEventArgs> tempChangedFiles = new Dictionary<String, FileSystemEventArgs>();

            lock (m_ChangedFiles)
            {
                foreach (KeyValuePair<string, FileSystemEventArgs> changedFile in m_ChangedFiles)
                {
                    tempChangedFiles.Add(changedFile.Key, changedFile.Value);
                }
                m_ChangedFiles.Clear();
            }

            foreach (KeyValuePair<string, FileSystemEventArgs> changedFile in tempChangedFiles)
            {
                m_FileSystemEventHandler(this, changedFile.Value);
            }
        }
    }
}

使用方式如下：

        s_DelayFileSystemWatcher = new DelayFileSystemWatcher(@"C:\Temp", "*.xml", fileSystemWatcher_Changed, 1500);

        private static void fileSystemWatcher_Changed(object sender, FileSystemEventArgs e)
        {
            switch (e.ChangeType)
            {
                case WatcherChangeTypes.Created:
                    //TODO
                    break;
                case WatcherChangeTypes.Deleted:
                    //TODO                        
                    break;
                case WatcherChangeTypes.Changed:
                    //TODO
                    break;
                default:
                    break;
            }
        }