Visual Basic® 2008 Programmer's Reference

Chapter 25. OOP Concepts

This chapter explains the fundamental ideas behind object-oriented programming (OOP). It describes the three main features of OOP languages: encapsulation, inheritance, and polymorphism. It explains the benefits of these features and describes how you can take advantage of them in Visual Basic.

This chapter also describes method overloading. In a sense, overloading provides another form of polymorphism. It lets you create more than one definition of the same class method, and Visual Basic decides which version to use based on the parameters the program passes to the method.

Many of the ideas described in this chapter will be familiar to you from your experiences with forms, controls, and other building blocks of the Visual Basic language. Those building blocks are object-oriented constructs in their own rights, so they provide you with the benefits of encapsulation, inheritance, and polymorphism whether you knew about them or not.

Classes

A class is a programming entity that gathers all the data and behavior that characterizes some sort of programming abstraction. It wraps the abstraction in a nice, neat package with well-defined interfaces to outside code. Those interfaces determine exactly how code outside of the class can interact with the class. A class determines which data values are visible outside of the class and which are hidden. It determines the routines that the class supports and their availability (visible or hidden).

A class defines properties, ...