Why Does FileSystemWatcher's Changed Event Fire Multiple Times for a Single File Modification?

Understanding Multiple FileSystemWatcher Changed Events

This article addresses a common issue with the FileSystemWatcher class: multiple "Changed" events triggered by a single file modification.

The Problem:

Why does modifying a text file sometimes generate two or more Changed events in FileSystemWatcher?

The Explanation:

This behavior is a known quirk of FileSystemWatcher. Applications like Notepad, when saving a file, often perform two distinct operations: writing the file's content and then updating its metadata (attributes). Each of these actions can generate a separate "Changed" event.

Important Considerations:

• Simply adjusting the NotifyFilter property may not always prevent multiple events. More sophisticated filtering or workarounds might be necessary.
• For advanced techniques and troubleshooting tips, consult this archived resource: FileSystemWatcher Tips.
• Always design your event handling logic to account for the possibility of multiple events to avoid redundant processing.

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