FileSystemWatcher not firing events

Question

For some reason, my FileSystemWatcher is not firing any events whatsoever. I want to know any time a new file is created, deleted or renamed in my directory. _myFolderPath is being set correctly, I have checked.

Here is my current code:

public void Setup() { var fileSystemWatcher = new FileSystemWatcher(_myFolderPath); fileSystemWatcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName; fileSystemWatcher.Changed += FileSystemWatcherChanged; fileSystemWatcher.Created += FileSystemWatcherChanged; fileSystemWatcher.Deleted += FileSystemWatcherChanged; fileSystemWatcher.Renamed += FileSystemWatcherChanged; fileSystemWatcher.Filter = "*.*"; fileSystemWatcher.EnableRaisingEvents = true; } private void FileSystemWatcherChanged(object sender, FileSystemEventArgs e) { MessageBox.Show("Queue changed"); listBoxQueuedForms.Items.Clear(); foreach (var fileInfo in Directory.GetFiles(_myFolderPath, "*.*", SearchOption.TopDirectoryOnly)) { listBoxQueuedForms.Items.Add(fileInfo)); } }

What have you done to verify that a situation occurs in which those events should fire? — tnw
– tnw, Commented Apr 29, 2013 at 12:37
I have manually created, renamed and deleted files in my directory. Nothing fires. — gwin003
– gwin003, Commented Apr 29, 2013 at 12:37
Local drive, its an AppData/Roaming folder to be more specific — gwin003
– gwin003, Commented Apr 29, 2013 at 12:39
Are you sure _myFolderPath is the correct path? Because your code seems quite okay, fairly similar to the sample at msdn.microsoft.com/en-us/library/… — pyrocumulus
– pyrocumulus, Commented Apr 29, 2013 at 12:39

Chris · Accepted Answer · 2013-04-29 12:51:28Z

62

You seem to be creating the FileSystemWatcher as a local variable in the setup method. This will of course go out of scope at the end of the method and may well be getting tidied up at that point, thus removing the watches.

Try creating the FSW at a point where it will be persisted (eg a program level variable) and see if that sorts you out.

answered Apr 29, 2013 at 12:51

Chris

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7 Comments

gwin003 Over a year ago

I moved the FileSystemWatcher to a private local variable and it seems to be working more consistently now.

Fredrik Mörk Over a year ago

@gwin003 It was a local variable. I suspect you mean that you moved it to a private field?

gwin003 Over a year ago

Oops, yeah thats what I meant haha. It wont let me edit my comment now for some reason...

Chris Over a year ago

You can only edit comments for a limited amount of time afterwards (5 mins I think). Glad that helped though. Another point to note with FSW is that they can't fire events on networked drives. Not relevant for you now from the comments above but a big gotcha if you ever do want to. :)

Chris Over a year ago

@adospace: stackoverflow.com/questions/298261/…

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Luca Ziegler · Accepted Answer · 2017-03-01 10:14:06Z

39

Use this setter to enable the trigger:

watcher.EnableRaisingEvents = true;

answered Mar 1, 2017 at 10:14

Luca Ziegler

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4 Comments

David Haxton Over a year ago

Oh my, thanks so much for that. Amazes me that that a flag is required for events.

the berserker Over a year ago

Oh, wow... That took an hour of my life :/ Strange choice to set it to false by default. Aren't the events like a primary thing why you'd want to use the FileSystemWatcher in the first place?

osiris Over a year ago

@theberserker, i think defaulting to false is the wisest choice because one may want to setup the watcher at a given time but only enable it after doing other setup work.

Bill Tarbell Over a year ago

I appreciate you posting this even though the OP had it in their code already. It definitely helps the rest of us that didn't notice the requirement.

MoMo · Accepted Answer · 2018-05-30 15:49:22Z

My problem was that I expected certain actions to cause the FileSystemWatcher Changed event to fire. For example, moving a file (clicking and dragging) from the desktop to the watched location did not raise an event but copying an existing file and pasting a new copy of it (there by creating a new file to the file system and not simply moving an existing one) caused the Changed event to be raised.

My solution was to add every NotifyFilter to my FileSystemWatcher. This way I am notified in all cases where the FileSystemWatcher is able to notify me.

NOTE that it isn't entirely intuitive/obvious as to which filters will notify you for specific cases. For example, I expected that if I included FileName that I would be notified of any changes to an existing file's name...instead Attributes seem to handle that case.

watcher.NotifyFilter = NotifyFilters.Attributes | NotifyFilters.CreationTime | NotifyFilters.FileName | NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.Size | NotifyFilters.Security;

Anatolii Humennyi · Accepted Answer · 2020-08-23 19:50:26Z

My issue was that I expected it watches subdirectories also but it doesn't do it by default. If you would like to monitor also subdirectories then set IncludeSubdirectories property to true (it's false by default):

fileSystemWatcher.IncludeSubdirectories = true;

Randy Kroeger · Accepted Answer · 2023-03-03 17:22:13Z

I had the same issue in that a move or copy paste of a file would not trigger the file watcher. However, if I renamed or altered the file within the directory it worked. I reviewed documentation (https://learn.microsoft.com/en-us/dotnet/api/system.io.filesystemwatcher?view=net-7.0) and it did not jump out what could cause this issue. Finally, there was a hint that maybe folder security because I read about how folder security could be different. I then went into folder security and the advanced settings. I gave permissions to Auditing to my user account. I also added my user account to Effective Access. Then, it all worked. I could move and cut/paste the file. Filewatcher now responded. This is what made the difference for me.

Jonas_Hess · Accepted Answer · 2016-08-23 08:57:28Z

We just had a very similar problem, where moving a folder did not trigger the expected events. The solution was to hard copy the entire folder, rather than just moving it.

DirectoryCopy(".", ".\\temp", True) Private Shared Sub DirectoryCopy( _ ByVal sourceDirName As String, _ ByVal destDirName As String, _ ByVal copySubDirs As Boolean) ' Get the subdirectories for the specified directory. Dim dir As DirectoryInfo = New DirectoryInfo(sourceDirName) If Not dir.Exists Then Throw New DirectoryNotFoundException( _ "Source directory does not exist or could not be found: " _ + sourceDirName) End If Dim dirs As DirectoryInfo() = dir.GetDirectories() ' If the destination directory doesn't exist, create it. If Not Directory.Exists(destDirName) Then Directory.CreateDirectory(destDirName) End If ' Get the files in the directory and copy them to the new location. Dim files As FileInfo() = dir.GetFiles() For Each file In files Dim temppath As String = Path.Combine(destDirName, file.Name) file.CopyTo(temppath, False) Next file ' If copying subdirectories, copy them and their contents to new location. If copySubDirs Then For Each subdir In dirs Dim temppath As String = Path.Combine(destDirName, subdir.Name) DirectoryCopy(subdir.FullName, temppath, true) Next subdir End If End Sub

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