Dependency management is one of those topics that quietly shapes the quality of every C# codebase. Get it right, and your system stays testable, readable, and flexible. Get it wrong and you inherit hidden coupling, brittle tests, and painful refactors. In this post, I break down the most common dependency patterns in .NET, from the ones you should reach for by default to the ones that should make you pause, and a few you should avoid unless you have no other choice.