What is the real difference between “Bastard Injection” and “Poor Man's Injection”

Question

From the \"Dependency Injection in .Net\" book I know that the object graph should be created at the Composition Root of the application which makes a lot o

Answer 1

Some notes to the part 2) of the question.

If you still need to register all the dependencies in the IoC container vs. coding them by hand in the exact same Composition Root, what's the real benefit of using an IoC container?

• If you have a tree of dependencies (clasess which depend on dependencies which depend on other dependencies and so on): you can't do all the "news" in a composition root, because you new up the instances on each "bastard injection" constructor of each class, so there are many "composition roots" spreaded along your code base

• Wheter you have a tree of dependencies, or not, using an IoC container will spare typing some code. Imagine you have 20 different classes that depend on the same IDependency. If you use a container you can provide a configuration to let it know which instance to use for IDependency. You'll make this in a single place, and the container will take care to provide the instance in all dependent classes

• The container can also control the object lifetime, which offers another advantage.

All of this, apart of the other obvious advantages provided by DI (testability, maintainability, code decouplig, extensibility...)