FileSystemWatcher Changed事件被引发两次

我有一个应用程序，我正在寻找一个文本文件，如果对文件做了任何更改，我使用OnChanged事件处理程序来处理事件。我正在使用NotifyFilters。LastWriteTime，但是事件仍然被触发两次。这是代码。

public void Initialize()
{
   FileSystemWatcher _fileWatcher = new FileSystemWatcher();
  _fileWatcher.Path = "C:\\Folder";
  _fileWatcher.NotifyFilter = NotifyFilters.LastWrite;
  _fileWatcher.Filter = "Version.txt";
  _fileWatcher.Changed += new FileSystemEventHandler(OnChanged);
  _fileWatcher.EnableRaisingEvents = true;
}

private void OnChanged(object source, FileSystemEventArgs e)
{
   .......
}

在我的情况下，OnChanged被调用两次，当我改变文本文件version.txt并保存它。

当前回答

我们可以这么简单。这对我很管用。

private static void OnChanged(object sender, FileSystemEventArgs e) 
{
    if (File.GetAttributes(e.FullPath) == FileAttributes.Directory)
        return;
    double timeSpan = DateTime.Now.Subtract(File.GetLastWriteTime(e.FullPath)).TotalSeconds;
    if (timeSpan > 1)
        return;
    Console.WriteLine($"Changed: {e.FullPath}");
}

2021-10-20 15:17:10

其他回答

我已经在我的委托中使用以下策略“修复”了这个问题:

// fsw_ is the FileSystemWatcher instance used by my application.

private void OnDirectoryChanged(...)
{
   try
   {
      fsw_.EnableRaisingEvents = false;

      /* do my stuff once asynchronously */
   }

   finally
   {
      fsw_.EnableRaisingEvents = true;
   }
}

2010-05-06 11:53:42

一个可能的“黑客”是使用响应式扩展来限制事件，例如:

var watcher = new FileSystemWatcher("./");

Observable.FromEventPattern<FileSystemEventArgs>(watcher, "Changed")
            .Throttle(new TimeSpan(500000))
            .Subscribe(HandleChangeEvent);

watcher.EnableRaisingEvents = true;

在本例中，我将设置为50ms，在我的系统上这就足够了，但更高的值应该更安全。(就像我说的，这仍然是一个“hack”)。

2014-02-10 06:54:06

我用了n种更简单的方法。

布尔-如果正在进行某项操作，则为true。当它结束时，false。在处理之前，将其添加到HashSet。这样我就不会重复元素了。每隔30分钟，计时器的事件就会运行一次，如果没有作业正在执行，它就会清除列表(just hashset = new hashset)。

2019-12-17 21:36:13

主要是为了未来的我:)

我用Rx写了一个包装器:

 public class WatcherWrapper : IDisposable
{
    private readonly FileSystemWatcher _fileWatcher;
    private readonly Subject<FileSystemEventArgs> _infoSubject;
    private Subject<FileSystemEventArgs> _eventSubject;

    public WatcherWrapper(string path, string nameFilter = "*.*", NotifyFilters? notifyFilters = null)
    {
        _fileWatcher = new FileSystemWatcher(path, nameFilter);

        if (notifyFilters != null)
        {
            _fileWatcher.NotifyFilter = notifyFilters.Value;
        }

        _infoSubject = new Subject<FileSystemEventArgs>();
        _eventSubject = new Subject<FileSystemEventArgs>();

        Observable.FromEventPattern<FileSystemEventArgs>(_fileWatcher, "Changed").Select(e => e.EventArgs)
            .Subscribe(_infoSubject.OnNext);
        Observable.FromEventPattern<FileSystemEventArgs>(_fileWatcher, "Created").Select(e => e.EventArgs)
            .Subscribe(_infoSubject.OnNext);
        Observable.FromEventPattern<FileSystemEventArgs>(_fileWatcher, "Deleted").Select(e => e.EventArgs)
            .Subscribe(_infoSubject.OnNext);
        Observable.FromEventPattern<FileSystemEventArgs>(_fileWatcher, "Renamed").Select(e => e.EventArgs)
            .Subscribe(_infoSubject.OnNext);

        // this takes care of double events and still works with changing the name of the same file after a while
        _infoSubject.Buffer(TimeSpan.FromMilliseconds(20))
            .Select(x => x.GroupBy(z => z.FullPath).Select(z => z.LastOrDefault()).Subscribe(
                infos =>
                {
                    if (infos != null)
                        foreach (var info in infos)
                        {
                            {
                                _eventSubject.OnNext(info);
                            }
                        }
                });

        _fileWatcher.EnableRaisingEvents = true;
    }

    public IObservable<FileSystemEventArgs> FileEvents => _eventSubject;


    public void Dispose()
    {
        _fileWatcher?.Dispose();
        _eventSubject.Dispose();
        _infoSubject.Dispose();
    }
}

用法:

var watcher = new WatcherWrapper(_path, "*.info");
// all more complicated and scenario specific filtering of events can be done here    
watcher.FileEvents.Where(x => x.ChangeType != WatcherChangeTypes.Deleted).Subscribe(x => //do stuff)

2017-09-05 21:13:24

我知道这是一个老问题，但我遇到了同样的问题，上面的解决方案都没有真正解决我所面临的问题。我已经创建了一个字典，它将文件名与LastWriteTime映射。因此，如果文件不在字典中，将继续执行该进程，否则将检查最后一次修改时间是什么时候，如果与字典中的时间不同，则运行代码。

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

        private void OnChanged(object source, FileSystemEventArgs e)
            {
                if (!dateTimeDictionary.ContainsKey(e.FullPath) || (dateTimeDictionary.ContainsKey(e.FullPath) && System.IO.File.GetLastWriteTime(e.FullPath) != dateTimeDictionary[e.FullPath]))
                {
                    dateTimeDictionary[e.FullPath] = System.IO.File.GetLastWriteTime(e.FullPath);

                    //your code here
                }
            }

2016-03-18 13:45:39

FileSystemWatcher Changed事件被引发两次

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