Why Does My FileSystemWatcher's OnChanged Event Fire Twice?

Troubleshooting Double-Triggered FileSystemWatcher OnChanged Events

Monitoring text files with FileSystemWatcher often results in the OnChanged event firing twice after a single modification. This is a known issue with the FileSystemWatcher class. The class documentation explains that multiple events can be triggered by a single file system action, especially with applications like Notepad that perform multiple disk writes.

Workaround: Filtering Duplicate Events

While the NotifyFilter property might offer some help, effective duplicate filtering usually requires manual implementation. Consider these strategies:

1. Timestamp/Unique Identifier: Use a timestamp or unique identifier to distinguish between actual file changes and duplicate events.
2. Event Tracking: Employ a dictionary or hash table to track recently processed events, preventing redundant processing.

Further Resources and Alternatives

• Explore this archived resource for further troubleshooting tips on FileSystemWatcher problems: [archived page](https://www.php.cn/link/8425bc94a44e3d1bb3c8c026b2702c00)
• Consider alternative file monitoring solutions or libraries providing finer-grained control over event handling and duplicate event suppression.

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