VB.NET Language in a Nutshell, Second Edition

Accessibility in Class Modules

The notion of accessibility (or scope) in class modules is more involved than it is in standard modules. As far as local variables (block-level and procedure-level) are concerned, there is no difference — we have block scope and procedure-level scope.

However, members of a class module can be assigned one of the following access modifiers:

• Public

• Private

• Friend

• Protected

• Protected Friend

(For standard modules, only Public, Private, and Friend are allowed.)

Actually, we can dispense with the Protected Friend modifier in one statement: Protected Friend is equivalent to Protected or Friend. Put another way, if Protected sets a specific range of accessibility (or inheritance — see below) and Friend sets a different range, then Protected Friend sets accessibility to the union of those ranges — if a member falls into either range, it passes the accessibility (or inheritance) criterion.

Note that class modules themselves can be declared with any one of the three access modifiers: Public, Private, or Friend (Protected is not allowed). When a class module declaration specifies one of these access modifiers, this simply restricts all of its members to that level of access, unless a member’s access is further restricted by the access modifier on the member declaration itself. For instance, if the class has Friend access, no member can have Public access. (Put another way, the Public access is overridden by the Friend class access.)

On the other hand, ...