Dependency Injection Overuse in C#: A Clear Critique

Dependency Injection (DI) is widely touted as a best practice in modern C# development. It promises looser coupling, easier testing, and flexible architecture. Frameworks like ASP.NET Core encourage DI by default, making it almost synonymous with “proper” C# design. However, this popular technique is often applied even when it adds no real benefit. In reality, the overuse of DI can introduce needless complexity and pitfalls that outweigh its theoretical advantages.

• Unnecessary Complexity: Rigidly using DI everywhere often means creating extra layers of interfaces and classes with little purpose beyond following the pattern. This adds boilerplate and duplication, violating the YAGNI (“You Aren’t Gonna Need It”) principle and lowering the readability and maintainability of the codebase. In cases where there is only one possible implementation of a dependency, forcing an interface abstraction provides “no real abstraction and zero value” – it merely makes the code harder to navigate.

• Performance Overhead: A DI container can incur runtime costs. It typically uses reflection and dynamic resolution to assemble objects, which can slow down application startup. Every dependency must be discovered and injected, sometimes via proxy objects, adding overhead. Moreover, debugging becomes more difficult when using a DI framework. The wiring of dependencies is hidden inside a “black box” container, so you cannot easily trace how components are constructed at runtime. This lack of transparency makes pinpointing issues harder, since the flow of control is obscured by the framework.

• Overkill for Simple Apps: Not every project gains from DI’s complexity. In a small or straightforward application with only a few components, using a full DI framework is often over-engineering. Even experts note that “for small projects where there aren't a lot of moving parts, there's little reason to use a DI framework.” In many cases, simple, direct instantiation of dependencies in code would be clearer and more efficient. Introducing a DI container “just because” can create indirection without any real payoff when interchangeable modules or extensive testing seams aren’t actually needed.

Dependency Injection is a powerful pattern but not a one-size-fits-all solution. Blindly adopting DI in every C# project can lead to unnecessary complexity and confusion. Developers should evaluate when DI truly adds value (such as in large, modular systems) and when a simpler approach would suffice. The best code design is achieved by using such advanced techniques judiciously – not by treating them as sacrosanct doctrine. Each tool, including DI, has its place; understanding its costs as well as its benefits is key to writing clear and effective C# code.