FileSystemWatcher does not report changes in a locked file

Question

I\'m monitoring a folder using a FileSystemWatcher like this:

watcher = new FileSystemWatcher(folder);
watcher.NotifyFilter = NotifyFilters.Size;
watcher.Cha         


        

Answer 1

Looks like the file data is cached and not actually written. When you write something to the file, the data is first placed to cache using certain file system IRP (driver request). Now when the data is actually written to the disk, another IRP is sent. It can be (this is a guess) that FileSystemWatcher catches only second IRP type.

The solution (if possible) is to call Flush on the file you are writing. If you are tracking changes made by other applications, things can become more complicated, of course.