Visual Basic 2005 in a Nutshell, Third Edition

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Chapter 8: Delegates and Events

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

' ----- First, try it in ascending order.

FlexSort(AddressOf SortAscending, dataValues)

For counter = 0 To 3

Debug.WriteLine(CStr(dataValues(counter)))

Next counter

Debug.WriteLine("")

' ----- Next, sort them again in descending order.

FlexSort(AddressOf SortDescending, dataValues)

For counter = 0 To 3

Debug.WriteLine(CStr(dataValues(counter)))

Next counter

End Sub

The output is:

2

4

6

9

9

6

4

2

Events and Event Binding

An event indicates some type of action. This action can be initiated by the user

(such as through a mouse click on a command button), by the application code

(such as when a change is made to a database record), or by the operating system

(such as a timer event). When any action like this occurs, it causes an event to be

raised or fired.

Each event has a source. This is the object to which the action is applied, such as

the button that was clicked. The source is responsible for alerting the operating

system that an event has occurred. It does so by sending an event notification

message. For this reason, the event source is often referred to as the sender.

An event often has an event argument, a means of conveying data that pertains to

the event. For instance, the press of a keyboard key generates an event that

includes event arguments describing ...