Part 3. Pure DI

In chapter 1, we gave a short outline of the three dimensions of DI: Object Composition, Lifetime Management, and Interception. In this part of the book, we’ll explore these dimensions in depth, providing each with their own chapter. Many DI Containers have features that directly relate to these dimensions. Some provide features in all three dimensions, whereas others only support some of them.

Because a DI Container is an optional tool, we feel it’s more important to explain the underlying principles and techniques that containers typically use to implement these features. Given this, part 3 examines how to apply DI without using a DI Container at all. A practical do-it-yourself guide, this is what we call Pure DI.

Chapter 7 explains how to compose objects in various frameworks like ASP.NET Core MVC, Console Applications, and so on. Not all frameworks support DI equally well, and even among those that do, the details differ a lot. For each framework, it can be difficult to identify the Seam that enables DI. Once that Seam is found, however, you have a solution for all applications that use that particular framework. In chapter 7, we’ve done this work for the most common .NET application frameworks. Think of it as a catalog of framework Seams.