Visual Basic 2005 in a Nutshell, Third Edition

OOP Development in Visual Basic | 35

OOP

This is the Title of the Book, eMatter Edition

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

Instance Members Versus Shared Members

Members of a class can either be instance members or shared members. Instance

members are only useful in a specific instance of the class, that is, from an object.

Until an instance of the object exists, these members cannot be used or refer-

enced in any way. Instance members belong to specific instances of the class

instead of to the class as a whole. The members added to the sample

Person class

above are all instance members.

Public Class SimpleClass

' ----- This is an instance member.

Public Comment As String

End Class

...

' ----- In some other code.

Dim myInstnace = New SimpleClass

myInstance.Comment = "I am not shared!"

Shared members (sometimes called static members) can be accessed without the

presence of any particular instance of the class. They belong to the whole class,

but they are also “shared” among all instances of the class. Shared members are

accessed by qualifying the name of the member with the name of the class.

Public Class SimpleClass

' ----- This is an instance member.

Public Shared Comment As String

End Class

...

' ----- In some other code.

SimpleClass.Comment = "I am shared!"

All members of a Module are automatically shared, even though the Shared

keyword is not used on each member of the ...