Windows Developer Power Tools

18.7 Obtaining a Decoupled Architecture with the Castle Windsor Container

When object-oriented programming languages were introduced, most programmers thought that all reusability problems had finally been solved. We now know this was far from true. The key principles to follow to achieve reusability are described next.

Loosely Coupled Design

This generally translates into not actively obtaining configuration and dependencies the class needs to function properly

Separation of Concerns

This dictates that a program should be broken into distinct services with little or no overlapping of responsibilities

Although it may seem like common sense, adhering to these principles can be difficult, and it’s easy to find examples where they are not applied. The end result is usually a system that is hard to maintain and hard to test, which gives newcomers an unpleasant sensation in their stomachs.

In these circumstances, Inversion of Control containers can come to the rescue. Inversion of Control—sometimes referred to simply as IoC—is a principle used mostly by frameworks. When you’re using an API, you have the normal invocation flow, as you are controlling the calls and the application. A framework, however, invokes the programmer’s code—thus the term “inversion of control.” IoC containers have adopted this principle to configure and prepare the classes registered in them.

The Castle Project offers a friendly and extensible IoC container called the Windsor Container. Several extensions come with it ...