Building Smart API Endpoints with C# Source Generators

Exposing CRUD endpoints for every model means writing the same boilerplate over and over. This post uses Roslyn source generators to auto-generate complete REST endpoints at compile-time — no runtime magic, no repetitive controllers — through a tool the author built called AutoApiGenerator.

What you’ll learn

• How the [AutoApi] attribute drives generation, including RoutePrefix and DbContextType options
• The generator pipeline: discovering annotated entities, analyzing their syntax/semantic models, and emitting a .gen.cs base plus a partial .cs for custom logic
• Wiring in EF Core for async, DI-backed CRUD with ID-based GET/{id}, PUT, and DELETE
• Extending or overriding generated behavior cleanly via partial classes
• A comparison of manual controllers, hand-coded minimal APIs, and the generator across boilerplate, customizability, type safety, and compile-time guarantees

The full source is on GitHub, so it’s a great read if you want to learn practical source-generator techniques you can adapt.