Lesson 16 - Abstract class, comparing and operator overloading in VB.NET
In the previous lesson, Type casting and object hierarchy in VB.NET, we learned about type casting and created an object hierarchy with a common ancestor in Visual Basic .NET. In today's tutorial, we're going to continue with that project.
An abstract class is a class whose instance does not make sense. Mainly because it is too vague, e.g. our Animal class. The point is to call on specific Animal descendants, e.g. a dog, so we won't actually instantiate the Animal class directly ever. In other words, it's better to prevent any instantiation of the class overall. To do that, we simply add the "MustInherit" modifier before the Animal class:
Public MustInherit Class Animal . . .
The program works the same as before, but if we try to create an instance of the Animal class, we'll get an error:
' this code won't work animals.Add(New Animal())
Other than preventing instantiation, abstract classes can do several other things
...End of the preview...
ict.social is a large database made up of manuals and tutorials, whose main goal is to provide high-quality IT education to everyone. We started out in the Czech republic, where we display roughly a million articles per month and receive plenty of gratitude from our users. Thanks to our successful establishment, we are now bringing these articles to the rest of the world.
Although we are trying to keep our content free of charge, maintaining the site is a huge effort for everyone involved. Therefore, some content (exercises and more advanced material) costs network points. Don't worry, they're really cheap :)
Requested article covers this content:
This tutorial explains abstract classes in Visual Basic. We'll learn about interfaces, implement custom comparing with IComparable, and overload operators.
Buying this article gives you unlimited access to it forever. You will learn some more and help us keep giving our site maintenance which helps you and others get better futures. It's a win-win.
You gain points by supporting our network. This is done by sending a helpful amount of money to support the site, or by creating content for the network.
You can get points immediately using:
|Credit card||SMS||Wire transfer|