Professional Visual Basic 2012 and .NET 4.5 Programming

Inheritance

Inheritance is the concept that a new class can be based on an existing class, inheriting the interface and functionality from the original class. In Chapter 3, you explored the relationship between a class and an object, and saw that the class is essentially a template from which objects can be created. Inheritance is always through a single chain to the base Object class. While Visual Basic supports multiple interfaces, it does not support multiple inheritance.

While using objects is very powerful, a single object does not always provide all the capabilities you might like. In particular, in many cases a class only partially describes what you need for your object. You may have a class called Person, for instance, which has all the properties and methods that apply to all types of people, such as first name, last name, and birth date. While useful, this class probably does not have everything you need to describe a specific type of person, such as an employee or a customer. An employee would have a hire date and a salary, which are not included in Person, while a customer would have a credit rating, something neither the Person nor the Employee classes would need.

Without inheritance, you would probably end up replicating the code from the Person class in both the Employee and Customer classes so that they would have that same functionality as well as the ability to add new functionality of their own.

Inheritance makes it very easy to create classes for Employee