ShellItemChangeWatcher - Changed event is not raised for ChangeFilters.FolderDeleted

[omeryanar]

Describe the bug and how to reproduce

Changed event is not raised after permanent delete (SHIFT+DELETE) of a folder. I tested on Windows 11 with explicitly setting ChangeFilters.FolderDeleted and then AllDiskEvents, and then AllEvents. In all three cases, Changed event is not raised for ChangeType equals to FolderDeleted.

I debugged ShellItemChangeWatcher and see that MessageFilter of WatcherNativeWindow is not called with correct parameters. I checked the code and MSDN documentation, and everything seems correct.

https://learn.microsoft.com/en-us/windows/win32/api/shlobj_core/nf-shlobj_core-shchangenotifyregister

So, what do you think the problem might be? Where should I check?

What code is involved

ShellItemChangeWatcher shellItemChangeWatcher = new ShellItemChangeWatcher();
shellItemChangeWatcher.NotifyFilter = ChangeFilters.AllDiskEvents;
shellItemChangeWatcher.Changed += ShellItemChangeWatcher_Changed;

void ShellItemChangeWatcher_Changed(object sender, ShellItemChangeWatcher.ShellItemChangeEventArgs e)
{
if (e.ChangedItems.Length > 0)
{
Console.WriteLine($"ShellItemChangeWatcher: {e.ChangeType}: ");
foreach (var item in e.ChangedItems)
{
Console.WriteLine($"{item}");
}
}
}

shellItemChangeWatcher.Item = ShellFolder.Desktop;
shellItemChangeWatcher.IncludeChildren = true;
shellItemChangeWatcher.EnableRaisingEvents = true;

Expected behavior

After deleting a folder from the file system, Changed event is raised for e.ChangeType equals to FolderDeleted.

[dahall]

I just created the following test and it fired the event.

using var item = ShellItem.Open(testDirectory!);
var subDir = Path.Combine(testDirectory!, "SubDir");
Directory.CreateDirectory(subDir);

using var watcher = new ShellItemChangeWatcher(item) { NotifyFilter = ChangeFilters.AllDiskEvents };
var eventRaised = new TaskCompletionSource<bool>();
watcher.Changed += (s, e) =>
{
   if (e.ChangeType == ChangeFilters.FolderDeleted)
      eventRaised.TrySetResult(true);
};
watcher.EnableRaisingEvents = true;

Directory.Delete(subDir);

var result = await Task.WhenAny(eventRaised.Task, Task.Delay(5000));
Assert.That(result, Is.EqualTo(eventRaised.Task));
Assert.That(await eventRaised.Task, Is.True);

What is different with your setup from the test?

[omeryanar]

There are two differences in my setup:

1. Instead of watching testDirectory folder, try watching Desktop folder with includeChildren= true:

using var watcher = new ShellItemChangeWatcher(ShellFolder.Desktop, true) { NotifyFilter = ChangeFilters.AllDiskEvents };

2. Try deleting the folder from Windows Explorer with SHIFT+DELETE, not using Directory.Delete
   In this case, I see that FolderUpdated event is raised instead of FolderDeleted event:

[dahall]

Thanks for this. After some testing, the Desktop appears to be the problem. I have tested this with includeChildren assigned true and false, and with multiple parent directories. For example, this code works:

using var item = new ShellFolder(PInvoke.Shell32.KNOWNFOLDERID.FOLDERID_LocalDocuments);
var subDir = Path.Combine(item.FileSystemPath!, $"SubDir{Guid.NewGuid():N}");
Directory.CreateDirectory(subDir);

using ShellItemChangeWatcher watcher = new(item, true) { NotifyFilter = ChangeFilters.AllDiskEvents };
var eventRaised = new TaskCompletionSource<bool>();
watcher.Changed += (s, e) =>
{
   if (e.ChangeType == ChangeFilters.FolderDeleted)
      eventRaised.TrySetResult(true);
};
watcher.EnableRaisingEvents = true;

Directory.Delete(subDir);

var result = await Task.WhenAny(eventRaised.Task, Task.Delay(5000));
Assert.That(result, Is.EqualTo(eventRaised.Task));
Assert.That(await eventRaised.Task, Is.True);

but changing the first line to use FOLDERID_Desktop doesn't. Literally every other folder works. I have no idea.