![]() If you’re looking to handle multiple, different, events from a single/unique file, such as Created with Changed, then you could key the cache on the file name and event named, concatenated. Now actually handle file event var e = (FileSystemEventArgs) If (args.RemovedReason != CacheEntryRemovedReason.Expired) return Handle cache item expiring private void OnRemovedFromCache(CacheEntryRemovedArguments args) _memCache.AddOrGetExisting(e.Name, e, _cacheItemPolicy) Only add if it is not there already (swallow others) Add file event to cache for CacheTimeMilliseconds private void OnChanged( object source, FileSystemEventArgs e)ĭ(CacheTimeMilliseconds) Public BlockAndDelayExample( string demoFolderPath) Private const int CacheTimeMilliseconds = 1000 Private readonly CacheItemPolicy _cacheItemPolicy Note that I use AddOrGetExisting as a simple way to block any additional events firing within the cache period being added to the cache. When it expires, the callback OnRemovedFromCache completes the behaviour intended for that file event.But instead of completing the desired action, it stores the event in Memor圜ache with a 1 second expiration and a CacheItemPolicy callback setup to execute on expiration. A file event (changed in the example below) is triggered.I worked on a nice little idea with a colleague, Ross Sandford, utilising Memor圜ache as a buffer to ‘throttle’ additional events. Good use of NotifyFilters ( see my post on how to select NotifyFilters) can help but there are still plenty of scenarios, like those above, where additional events will still get through for a file system event. This will fire twice if I edit a file in NotepadĬomplete Console applications for both are available on Github. ![]() Private static void OnChanged( object source, FileSystemEventArgs e) Public ExampleAttributesChangedFiringTwice( string demoFolderPath) If you edited a text file in c:\temp, you would get 2 events firing.Ĭlass ExampleAttributesChangedFiringTwice For the purposes of this article, it makes for a convenient example to recreate. Example: Recreating Edit a File in Notepad Firing 2 EventsĪs stated above, we know that 2 events from this action would mark the start and end of a write, meaning we could just focus on the second, if we had full confidence, this would be the consistent behaviour. Likewise, some applications (for example, antivirus software) might cause additional file system events that are detected by FileSystemWatcher. Moving a file is a complex operation that consists of multiple simple operations, therefore raising multiple events. For example, when a file is moved from one directory to another, several OnChanged and some OnCreated and OnDeleted events might be raised. See also, MSDN documentation:Ĭommon file system operations might raise more than one event. However, FileSystemWatcher cannot make any promises to behave predictably for all OS and application behaviours. Try it with a very large file to see for yourself. Note that in some scenarios, like the example used below, the first event will be the start of the file writing and the second event will be the end, which, while not documented behaviour, is at least predictable.
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