Yep. If you do something in an Accepting handler you need to set Cancel to indicate that.

Originally posted by @tig in #4022

I goofed in using CancelEventArgs as "Handled" just makes more sense in most cases.

Related:

• IsDefault on button makes it click itself on close #3913

Fix is straight forward but will touch a ton of files:

-public class CommandEventArgs : CancelEventArgs
+public class CommandEventArgs : HandledEventArgs