Dependency Injection: A Practical Introduction

We all want to build code that is maintainable and easily testable. Dependency Injection can help us get there. But what is Dependency Injection? The answers to the question seem to cause more confusion than help. We'll start with the basics to see what Dependency Injection is, why we want to use it, and how we can add it to our applications. Be prepared to spend a lot of time in code. After we have a good handle on the how all of the pieces fit together, we'll see how a DI container (such as Unity or Ninject) can make things even easier.