Hi @Jun_Wang,
sender
and e
are standard parameters that are passed to any event handler, where:
sender
contains a reference to the control/object that raised the event .e
contains the event data. The contents ofe
depend on the event that was triggered.
More info: Handling and Raising Events - .NET | Microsoft Learn
This is true. The sample code is adding an event handler (e.g. delegate) to the event’s list of handlers. An event can notify more than one event handler.
– Dale