This book is not a treatment of the theory of design patterns. We show design patterns applied in real-world architectural scenarios so that you can see them in action and see the benefits that they bring. It explains why it's worth spending time building design patterns into your applications, even though this may seem at odds with Rapid Application Development. After a fast-paced introduction to design patterns, the core of this book consists of three case studies, which show how design patterns are applied in each of the main tiers of an application: the data, business, and presentation layers. These case studies flesh out the reader's understanding of design patterns, and show how they can be employed in real scenarios that will be instantly recognizable to all VB .NET programmers. The book also shows how design patterns can be used in conjunction with .NET Remoting, so that they can be applied not just within individual tiers, but across them as well. Since many VB .NET programmers may not be completely familiar with UML, we also provide a UML primer as an appendix.