Fix NullReferenceException

martincostello · web-flow · commit 8c1227b6dd7c · 2024-04-08T14:02:32.000+01:00
Fix NullReferenceException in FileSystemWatcher on Windows if two threads try and dispose the instance at the same time.
diff --git a/src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.Win32.cs b/src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.Win32.cs
@@ -105,7 +105,7 @@ private void StopRaisingEvents()
             // increased, such that the disposal operation won't take effect and close the handle
             // until that P/Invoke returns; if during that time the FSW is restarted, the IsHandleInvalid
             // check will see a valid handle, unless we also null it out.
-            _directoryHandle.Dispose();
+            _directoryHandle?.Dispose();
             _directoryHandle = null;
         }
 

Original file line number	Diff line number	Diff line change
`@@ -105,7 +105,7 @@ private void StopRaisingEvents()`
`105`	`105`	`// increased, such that the disposal operation won't take effect and close the handle`
`106`	`106`	`// until that P/Invoke returns; if during that time the FSW is restarted, the IsHandleInvalid`
`107`	`107`	`// check will see a valid handle, unless we also null it out.`
`108`		`- _directoryHandle.Dispose();`
	`108`	`+ _directoryHandle?.Dispose();`
`109`	`109`	`_directoryHandle = null;`
`110`	`110`	`}`
`111`	`111`