恐怕这是FileSystemWatcher类的一个众所周知的错误/特性。这是来自类的文档:

You may notice in certain situations that a single creation event generates multiple Created events that are handled by your component. For example, if you use a FileSystemWatcher component to monitor the creation of new files in a directory, and then test it by using Notepad to create a file, you may see two Created events generated even though only a single file was created. This is because Notepad performs multiple file system actions during the writing process. Notepad writes to the disk in batches that create the content of the file and then the file attributes. Other applications may perform in the same manner. Because FileSystemWatcher monitors the operating system activities, all events that these applications fire will be picked up.

现在这段文本是关于Created事件的，但同样的事情也适用于其他文件事件。在一些应用程序中，您可能能够通过使用NotifyFilter属性来解决这个问题，但我的经验是，有时您还必须进行一些手动重复过滤(hacks)。

前段时间我书签了一个页面，里面有一些FileSystemWatcher技巧。你可能会想去看看。

恐怕这是FileSystemWatcher类的一个众所周知的错误/特性。这是来自类的文档:

You may notice in certain situations that a single creation event generates multiple Created events that are handled by your component. For example, if you use a FileSystemWatcher component to monitor the creation of new files in a directory, and then test it by using Notepad to create a file, you may see two Created events generated even though only a single file was created. This is because Notepad performs multiple file system actions during the writing process. Notepad writes to the disk in batches that create the content of the file and then the file attributes. Other applications may perform in the same manner. Because FileSystemWatcher monitors the operating system activities, all events that these applications fire will be picked up.

现在这段文本是关于Created事件的，但同样的事情也适用于其他文件事件。在一些应用程序中，您可能能够通过使用NotifyFilter属性来解决这个问题，但我的经验是，有时您还必须进行一些手动重复过滤(hacks)。

前段时间我书签了一个页面，里面有一些FileSystemWatcher技巧。你可能会想去看看。

In my case need to get the last line of a text file that is inserted by other application, as soon as insertion is done. Here is my solution. When the first event is raised, i disable the watcher from raising others, then i call the timer TimeElapsedEvent because when my handle function OnChanged is called i need the size of the text file, but the size at that time is not the actual size, it is the size of the file imediatelly before the insertion. So i wait for a while to proceed with the right file size.

private FileSystemWatcher watcher = new FileSystemWatcher();
...
watcher.Path = "E:\\data";
watcher.NotifyFilter = NotifyFilters.LastWrite ;
watcher.Filter = "data.txt";
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = true;

...

private void OnChanged(object source, FileSystemEventArgs e)
   {
    System.Timers.Timer t = new System.Timers.Timer();
    try
    {
        watcher.Changed -= new FileSystemEventHandler(OnChanged);
        watcher.EnableRaisingEvents = false;

        t.Interval = 500;
        t.Elapsed += (sender, args) => t_Elapsed(sender, e);
        t.Start();
    }
    catch(Exception ex) {
        ;
    }
}

private void t_Elapsed(object sender, FileSystemEventArgs e) 
   {
    ((System.Timers.Timer)sender).Stop();
       //.. Do you stuff HERE ..
     watcher.Changed += new FileSystemEventHandler(OnChanged);
     watcher.EnableRaisingEvents = true;
}

试试下面的代码:

class WatchPlotDirectory
{
    bool let = false;
    FileSystemWatcher watcher;
    string path = "C:/Users/jamie/OneDrive/Pictures/Screenshots";

    public WatchPlotDirectory()
    {
        watcher = new FileSystemWatcher();
        watcher.Path = path;
        watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
                               | NotifyFilters.FileName | NotifyFilters.DirectoryName;
        watcher.Filter = "*.*";
        watcher.Changed += new FileSystemEventHandler(OnChanged);
        watcher.Renamed += new RenamedEventHandler(OnRenamed);
        watcher.EnableRaisingEvents = true;
    }



    void OnChanged(object sender, FileSystemEventArgs e)
    {
        if (let==false) {
            string mgs = string.Format("File {0} | {1}",
                                       e.FullPath, e.ChangeType);
            Console.WriteLine("onchange: " + mgs);
            let = true;
        }

        else
        {
            let = false;
        }


    }

    void OnRenamed(object sender, RenamedEventArgs e)
    {
        string log = string.Format("{0} | Renamed from {1}",
                                   e.FullPath, e.OldName);
        Console.WriteLine("onrenamed: " + log);

    }

    public void setPath(string path)
    {
        this.path = path;
    }
}

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;
   }
}

很多答案都令人震惊，真的。 这里有一些代码从我的XanderUI控件库修复这个问题。

private void OnChanged(object sender, FilesystemEventArgs e)
{
    if (FSWatcher.IncludeSubdirectories == true)
    {
        if (File.Exists(e.FullPath)) { DO YOUR FILE CHANGE STUFF HERE... }
    }
    else DO YOUR DIRECTORY CHANGE STUFF HERE...
}