API Versioning in ASP.NET Core with Custom Middleware
As APIs evolve, the need to introduce breaking changes becomes inevitable. The key challenge is to roll out these updates without disrupting existing clients who depend on the current contract. This is where API versioning comes in. While feature-rich libraries like Asp.Versioning.Http are excellent, understanding how to build your own versioning scheme with middleware gives you maximum control and a deeper appreciation for the ASP.NET Core pipeline.
In this post, we’ll explore a clean, middleware-based approach to API versioning using a custom request header. We’ll build a solution that inspects a header and transparently rewrites the request path to route to the correct endpoint implementation.
Why a Middleware Approach?
Dedicated versioning libraries are powerful, offering features like API explorer integration, version advertisement, and conventions. However, a custom middleware solution offers its own set of advantages:
- Full Control: You define the exact logic for how a version is resolved. You can read it from a header, a claim, a query string, or even a combination of factors.
- Lightweight: You add only the logic you need, without any extra overhead.
- Decoupled: The versioning logic lives in one place (the middleware) rather than being scattered across controllers with attributes. This can lead to cleaner endpoint definitions.
- Great for Learning: Building it yourself is a fantastic way to understand how the ASP.NET Core request pipeline and routing work …