Visual Basic 2005 in a Nutshell, Third Edition

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Chapter 8: Delegates and Events

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

Custom Events

New in 2005. Sometimes there may be a software need to exhibit more control

over the lifetime of an event in your classes. The 2005 release of Visual Basic adds

features that let you monitor and take action each time a handler is added to an

event, each time a handler is removed from an event, and each time an event is

raised. This new feature is called custom events.

Using these custom events is easy. In your class definition, simply type:

accessModifier Custom Event eventName

and press the Enter key. (accessModifier is one of the standard access modifiers,

like

Public, that can be used with events.) Visual Studio provides the outline of

the custom event.

accessModifier Custom Event eventName As EventHandler

AddHandler(ByVal value As EventHandler)

' ----- Special code when adding handlers.

End AddHandler

RemoveHandler(ByVal value As EventHandler)

' ----- Special code when removing handlers.

End RemoveHandler

RaiseEvent(ByVal sender As Object, ByVal e As System.EventArgs)

' ----- Special code when raising the event.

End RaiseEvent

End Event

These event handlers fire when the specific event-related action happens with the

eventName event.