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The Last Word
Three-tier design is an abstraction. No successful application will implement it exactly. However, it's also a powerful guideline that helps you shape how classes interact in your application. It may seem strange to start talking about DataSets and business objects in a book on user interface design. (In fact, there are other excellent .NET books written entirely about data access.) But as you'll see, when you set specific rules about how the user interface tier can communicate with other parts of your program, you start to make the transition from a simple collection of objects to a true user interface framework.
The following chapters of this book focus on mastering the tools of .NET user interfaces. Considerations for design and user interface architecture crop up periodically, but they take a back seat to the amazing new programming model of .NET. This chapter was designed to give you the background in application architecture that you need to understand this "other layer." If you keep the considerations of this chapter in mind as you continue reading, you'll discover an entirely new and richer way to program user interfaces.
This chapter also introduced you to the broad picture of user interface in the .NET world, and the basic design assumptions that Visual Studio .NET makes automatically. These decisions can be altered, and the .NET framework itself allows you a considerable amount of freedom to create the exact framework that you want. In later chapters you'll learn how to exploit this freedom to create all types of custom controls.
