Chapter 23. Defining Classes and Their Properties

This book hasn't emphasized the fact, but you've been working with classes since the very beginning. The very first program you created in Lesson 1 included several classes, such as the program's main form and some behind-the-scenes classes that help get the program running. Since then, you've used all kinds of control classes — the MessageBox class, the Array class, collection classes, the Debug class, and more. You can even treat primitive data types such as Integer and String as classes under some circumstances.

In this lesson you learn how to create your own classes. You learn how to define a class and give it properties.

WHAT IS A CLASS?

A class defines a type of object. It defines the properties, methods, and events provided by its type of object. After you define a class, you can make as many instances of that class as you like.

For example, the Button class defines the properties and behaviors of a button user interface element. You can create any number of instances of Buttons and place them on your forms.

You can think of a class as a blueprint for making objects. When you create an instance of the class, you use the blueprint to make an object that has the properties and behaviors defined by the class. You can also think of a class as a cookie cutter. Once you've created the cookie cutter, you can make any number of cookies that all have the same shape.

Classes are very similar to the structures described in Lesson 17, and many ...

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