FileSystemWatcher fires multiple times for the same event

The FileSystemWatcher component recently gave me some headaches when firing events in response to changes to files it was watching.  In one case, when modifying a file, the FileSystemWatcher was firing four times for the same event… or so it seemed. After some research and testing, I came to the realization that four events were being fired. The FileSystemWatcher was doing it’s job right. I had simply disregarded the effects of anti-virus and native application file system handling. A simple change of a text file in Notepad may seem like only one file system event, but adding an anti-virus program’s checks into the mix can easily make that single event turn into four unique file system actions.

http://www.experts-exchange.com/Programming/Languages/.NET/Q_20708008.html