1.3. What to inject and what not to inject

In the previous section, I described the motivational forces that make us think about DI in the first place. If you’re convinced that loose coupling is a good idea, you may want to make everything loosely coupled. Overall, this is a good idea. When you must decide how to package modules, loose coupling provides especially useful guidance. You don’t have to abstract everything away and make everything pluggable. In this section, I’ll provide you with some decision tools that can help you decide how to model your DEPENDENCIES.

The .NET Base Class Library (BCL) consists of many assemblies. Every time you write code that uses a type from a BCL assembly, you add a dependency to your module. In the previous section, I discussed how loose coupling is important, and how programming to an interface is the cornerstone.