摘要：
使用System.Collections.Generic；使用System.Threading；namespaceUtility｛publicclassDelayFileSystemWatcher｛privatereadonlyTimerm_Timer；filter）；Timeout.Infinite）；
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;
}
}