fwatcher.Path = txtFolder.Text;

Type of changes to watch is set by the property NotifyFilter.

fwatcher.NotifyFilter=NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName;

Now the FileSystemwatcher is set to watch for changes in LastWrite, LastAccess and FileName.

Add event handlers to capture events like Changed, Created, Deleted and Renamed.

fwatcher.Changed += new FileSystemEventHandler(Changed);
fwatcher.Created += new FileSystemEventHandler(FileCreated);
fwatcher.Deleted += new FileSystemEventHandler(Deleted);
fwatcher.Renamed += new RenamedEventHandler(Renamed);

Files of a specific extension (like *.txt) can be watched by setting the Filter property to *.txt. This may be useful when you want to watch over the source code of a production box expect the log files. So that you can filter your watch by extensions.

The FileSystemWatcher can be programmatically controlled by enabling and disabling it using the EnableRaisingEvents property.

fwatcher.Filter = "*.txt";
fwatcher.EnableRaisingEvents = true;

Capturing the change

If we want to notify the administrator, that a file has been changed, we would require the name of the file to which the change has been made. To get the name of the file we use the event handler argument FileSystemEventArgs.

}

FullPath property of the FileSystemEventArgs gives the full path of the file to which the change has happened. This can be displayed in a label to notify the administrator.

Conclusion

FileSystemWatcher can be used to watch over files that contains sensitive information or source code that needs to be monitored for unauthorized changes. Although we can use Windows APIs to monitor a folder, using FileSystemWatcher class is simple and easy.