Chapter 14. Building Components
Components enable you to reuse application logic across multiple pages or even across multiple applications. For example, you can write a method named GetProducts() once and use the method in all the pages in your website. By taking advantage of components, you can make your applications easier to maintain and extend. For simple applications, there is no reason to take advantage of components. However, as soon as your application contains more than a few pages, you'll discover that you are repeating the same work over and over again. Whenever you discover that you need to write the same method more than once, you should immediately rip the method out of your page and add the method to a component. Classic ASP Note In classic ASP, programmers often used massive and difficult to maintain #INCLUDE files to create libraries of reusable subroutines and functions. In ASP.NET, you use components to build these libraries. In this chapter, you learn how to build components in the .NET framework. First, you are provided with an overview of writing components: You learn how to create simple components and use them in the pages in your application. In particular, you learn how to define component methods, properties, and constructors. You also learn how to take advantage of overloading, inheritance, and interfaces. Next, you learn how to build component libraries that can be shared across multiple applications. Different methods of compiling a set of components into assemblies are examined. You also learn how you can add a component library to the Global Assembly Cache. Finally, architectural issues involved in using components are discussed. The final section of this chapter shows you how to build a simple three-tiered application that is divided into distinct User Interface, Business Logic, and Data Access layers. Note Let's clarify the terminology. In this book, I use the word component as a synonym for the word class. Furthermore, by the word object, I mean an instance of a class. I am ignoring a special meaning for the word component in the .NET Framework. Technically, a component is a class that implements the System.ComponentModel.IComponent interface. I am ignoring this special meaning of the word component in favor of the common language use of the word. |
