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...
}

我必须结合以上文章中的几个想法，并添加文件锁定检查，让它为我工作:

FileSystemWatcher fileSystemWatcher;

private void DirectoryWatcher_Start()
{
    FileSystemWatcher fileSystemWatcher = new FileSystemWatcher
    {
        Path = @"c:\mypath",
        NotifyFilter = NotifyFilters.LastWrite,
        Filter = "*.*",
        EnableRaisingEvents = true
    };

    fileSystemWatcher.Changed += new FileSystemEventHandler(DirectoryWatcher_OnChanged);
}

private static void WaitUntilFileIsUnlocked(String fullPath, Action<String> callback, FileAccess fileAccess = FileAccess.Read, Int32 timeoutMS = 10000)
{
    Int32 waitMS = 250;
    Int32 currentMS = 0;
    FileInfo file = new FileInfo(fullPath);
    FileStream stream = null;
    do
    {
        try
        {
            stream = file.Open(FileMode.Open, fileAccess, FileShare.None);
            stream.Close();
            callback(fullPath);
            return;
        }
        catch (IOException)
        {
        }
        finally
        {
            if (stream != null)
                stream.Dispose();
        }
        Thread.Sleep(waitMS);
        currentMS += waitMS;
    } while (currentMS < timeoutMS);
}    

private static Dictionary<String, DateTime> DirectoryWatcher_fileLastWriteTimeCache = new Dictionary<String, DateTime>();

private void DirectoryWatcher_OnChanged(Object source, FileSystemEventArgs ev)
{
    try
    {
        lock (DirectoryWatcher_fileLastWriteTimeCache)
        {
            DateTime lastWriteTime = File.GetLastWriteTime(ev.FullPath);
            if (DirectoryWatcher_fileLastWriteTimeCache.ContainsKey(ev.FullPath))
            {
                if (DirectoryWatcher_fileLastWriteTimeCache[ev.FullPath].AddMilliseconds(500) >= lastWriteTime)
                    return;     // file was already handled
            }

            DirectoryWatcher_fileLastWriteTimeCache[ev.FullPath] = lastWriteTime;
        }

        Task.Run(() => WaitUntilFileIsUnlocked(ev.FullPath, fullPath =>
        {
            // do the job with fullPath...
        }));

    }
    catch (Exception e)
    {
        // handle exception
    }
}

解决方案实际上取决于用例。您是否在注意不更改的新文件，或每隔一段时间更改一次的文件或经常更改的文件?在我的情况下，它的变化不太频繁，我不想错过任何这些变化。

但是我也不想在写入过程尚未完成写入的地方发生更改事件。

在我的情况下，我注意到6 (6 !!)onchange事件写一个125字符的txt文件。

我的解决方案是民意调查和改变事件的混合，民意调查经常被消极地看待。正常轮询比较慢，比如每10秒一次，以防FileSystemWatcher (FSW)“错过”一个事件。轮询立即响应FSW更改事件。

关键是在FSW。更改事件时，轮询速度加快，例如每100毫秒，并等待直到文件稳定。因此我们有了“两阶段轮询”:阶段1比较慢，但在FSW文件更改事件时立即响应。第二阶段是快速的，等待一个稳定的文件。

如果FSW检测到多个文件更改，每个事件都会加速轮询循环，并有效地启动一个新的短等待周期。只有在轮询循环检测到上次写入时文件没有进一步的变化之后，它才假定文件是稳定的，并且您的代码可以处理更改后的文件。

我选择了10秒和100毫秒的超时，但是您的用例可能需要不同的超时值。

这里是轮询，其中AppConfig。fiIO是要注意的FileInfo:

private readonly EventWaitHandle ewhTimeout = new AutoResetEvent(false);

private void TwoPhasedPolling()
{
    bool WaitForChange = true; //false: wait until stable
    DateTime LastWriteTime = DateTime.MinValue;
    while (true)
    {
        // wait for next poll (timeout), or FSW event
        bool GotOne = ewhTimeout.WaitOne(WaitForChange ? 10 * 1000 : 100);
        if (GotOne)
        {
            // WaitOne interrupted: end of Phase1: FSW detected file change
            WaitForChange = false;
        }
        else
        {
            // WaitOne timed out: Phase2: check file write time for change
            if (AppConfig.fiIO.LastWriteTime > LastWriteTime)
            {
                LastWriteTime = AppConfig.fiIO.LastWriteTime;
            }
            else
            {
                // End of Phase2: file has changed and is stable
                WaitForChange = true;
                // action on changed file
                ... your code here ...
            }}}}

private void fileSystemWatcher1_Changed(object sender, FileSystemEventArgs e)
{
    ewhTimeout.Set();
}

NB:是的，我也不喜欢}}}}，但它使列表更短，这样你就不必滚动了:-)

我已经用一个类创建了一个Git repo，该类扩展了FileSystemWatcher，以便仅在复制完成时触发事件。它将丢弃除最后一个事件以外的所有已更改事件，仅在文件可读时才引发该事件。

下载FileSystemSafeWatcher并将其添加到项目中。

然后将其用作普通的FileSystemWatcher并在事件触发时进行监视。

var fsw = new FileSystemSafeWatcher(file);
fsw.EnableRaisingEvents = true;
// Add event handlers here
fsw.Created += fsw_Created;

试试这个，效果很好

  private static readonly FileSystemWatcher Watcher = new FileSystemWatcher();
    static void Main(string[] args)
    {
        Console.WriteLine("Watching....");

        Watcher.Path = @"D:\Temp\Watcher";
        Watcher.Changed += OnChanged;
        Watcher.EnableRaisingEvents = true;
        Console.ReadKey();
    }

    static void OnChanged(object sender, FileSystemEventArgs e)
    {
        try
        {
            Watcher.Changed -= OnChanged;
            Watcher.EnableRaisingEvents = false;
            Console.WriteLine($"File Changed. Name: {e.Name}");
        }
        catch (Exception exception)
        {
            Console.WriteLine(exception);
        }
        finally
        {
            Watcher.Changed += OnChanged;
            Watcher.EnableRaisingEvents = true;
        }
    }

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}");
}