Visual Basic.NET How to Program (PDF)

Chapter 8 Object-Based Programming 341
Purple box indicates
a method
Blue box preceded by a
lock indicates a Private
instance variable
Fig. 8.20 Class View of Fig. 8.1 and Fig. 8.2.
The second feature that Visual Studio provides is the Object Browser, which lists
the Framework Class Library (FCL) classes available in Visual Basic. Developers use the
Object Browser to learn about the functionality provided by a specific object. To open
the Object Browser, right click any Visual Basic class or method in the code editor and
select Go To Definition (Fig. 8.21). Figure 8.22 shows the Object Browser when the
user selects keyword Object in the code editor. Note that the Object Browser lists all
non-Private members provided by class Object in the Members of Object
window—this window offers developers “instant access” to information regarding the services
of various objects. Note also that the Object Browser lists in the Objects window
all objects that Visual Basic provides.
SUMMARY
Every class in Visual Basic is a derived class of Object.
Keywords Public and Private are member access modifiers.
Instance variables, properties and methods that are declared with member access modifier Public
are accessible wherever the program has a reference to an object of that class.
Instance variables, properties and methods that are declared with member access modifier Private
are accessible only to members of the class, such as other variables and methods.
Every instance variable, property or method definition should be preceded by a member access
modifier.
Private methods often are called utility methods, or helper methods, because they can be called
only by other methods of that class and are used to support the operation of those methods.
The creation of Public data in a class is an uncommon and dangerous programming practice.