What is ObjectBuilder?
ObjectBuilder is a library that was developed in early 2005 by the Microsoft patterns & practices team that was working on the Composite UI Application Block. It was born of a need for a dependency injection system that was flexible enough to support two very different uses in the present (CAB and Enterprise Library), and hopefully a variety of uses in the future.
Is ObjectBuilder a Dependency Injection container?
While ObjectBuilder can be used as a form of DI container, it is better described as a framework that allows you to build DI containers. The WorkItem class in CAB was the first DI container built from ObjectBuilder, and behaves like a combination service locator and object factory. The configuration system in Enterprise Library for VS2005 was the second DI container, and it behaves quite differently.
Using ObjectBuilder, it's possible to build DI containers that mimic a variety of existing containers.