FileSystemWatcher fires event without the file name

Question

I have a pet project I'm working on where the FileSystemWatcher is vexing me.

Here's the initialization code:

for (var xx = 0; xx < _roots.Count; xx++)
{
    var watcher = new FileSystemWatcher();
    var root = _roots[xx];

    watcher.Path = root;
    // watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName;
    watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName;

    watcher.Filter = "*.*";
    watcher.Changed += new FileSystemEventHandler(OnChanged);
    watcher.Created += new FileSystemEventHandler(OnChanged);
    watcher.Deleted += new FileSystemEventHandler(OnChanged);
    watcher.Renamed += new RenamedEventHandler(OnRenamed);

    watcher.EnableRaisingEvents = true;

    _rootWatchers.Add(watcher);
}

Let's say the root we're watching "c:\root" and there's a sub directory "c:\root\subdir" that contains a file called "file1.txt".

The watcher is up and running and I delete "file1.txt". When the handler is called and examine the values of FileSystemEventArgs.

I expect for e.Name == "file1.txt" and e.FullPath == "c:\\root\\subdir\\file1.txt.

The actual values are "subdir" and "c:\\root\\subdir".

I'm sure it's something simple I missed in the documentation somewhere.

Answer 1

You are correct, the issue you are facing is practically one of forgetting to set a property.

If you set watcher.IncludeSubdirectories = true;, you'll get notified about the file deletion even in deeper levels.

In the default mode, the FileSystemWatcher only records changes to the given directory. Sub-directories being modeled sort of directory entries similar to files, any additions/deletions inside them are just reported as changes directly to the sub-directories (you would see that if you checked the FileSystemEventArgs.ChangeType property in the OnChanged handler).

Even if you turn on sub-directories monitoring, you'll still get a change event (FileSystemEventArgs.ChangeType = WatcherChangeTypes.Changed) for the subdir directory as it is also modified when you delete a file inside it. That is in addition to the deletion event for the file.

My test code:

static void Main(string[] args)
{
    var watcher = new FileSystemWatcher();

    watcher.Path = @"C:\test_dir";
    // watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName;
    watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName;

    watcher.Filter = "*.*";
    watcher.Changed += new FileSystemEventHandler(OnChanged);
    watcher.Created += new FileSystemEventHandler(OnChanged);
    watcher.Deleted += new FileSystemEventHandler(OnChanged);
    watcher.Renamed += new RenamedEventHandler(OnRenamed);

    watcher.IncludeSubdirectories = true;

    watcher.EnableRaisingEvents = true;

    while (true)
    {
    }
}

private static void OnRenamed(object sender, RenamedEventArgs e)
{
    Console.WriteLine($"OnRenamed: {e.FullPath}, {e.OldFullPath}");
}

private static void OnChanged(object sender, FileSystemEventArgs e)
{
    Console.WriteLine($"OnChanged: {e.ChangeType}, {e.Name}[{e.FullPath}]");
}