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

The solution to the problem is not to open the files, but to actually READ from them. It's enough to read even one byte, and the Windows cache mechanism will write the contents of the file to the disk, thus allowing you to read them.

I ended up implementing a thread that went over all the files, opened them and read a byte from them. This caused them to change, and triggered the event in the FileSystemWatcher object.

The reason that Windows Explorer F5 works as well, is that Windows actually reads the contents of the file in order to show some extended contents (e.g., thumbnails). Once the file is being read, the cache first writes to the disk, triggering the event in the FSW.