Imagine you're working for a large enterprise that has many internal services. They expose databases, SOAP services, secret managers, REST endpoints, caches, messaging queues, and much more. You're tasked with modernizing an application that uses all these things. While your project is being modernized, some of those other services are also being modernized to very different service providers, and over time, it's all getting lifted to the cloud, where things may be different again. It's not enough to just register your interface/implementation pairs. You have to be able to completely decouple your dependencies. At the end of this session you'll understand what dependency injection is, what SOLID principles it applies to, and recognize how to decouple dependencies from your application through some intentional patterns. We'll go over all this in a 'back end' C# and .NET REST API.