Validation in API vs MVC (error response formatting)?

Short answer: [ApiController] handles automatic validation: Returns 400 BadRequest with ValidationProblemDetails if ModelState.IsInvalid. In MVC (without [ApiController]), you need to manually check ModelState.IsValid. if (!ModelState.IsValid) return View(model);

Real-world example (ShopNest)

A ShopNest checkout request flows through middleware, hits a minimal API or controller, uses scoped services, and returns ProblemDetails on errors.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.