How would you handle validation errors in a REST API?

Short answer: Use model validation with data annotations: public class UserModel

Example code

{ [Required] [EmailAddress] public string Email { get; set; }
} Return 400 Bad Request with a list of validation errors: { "status": 400, "error": "Validation Failed", "details": ["Email is required", "Password must be at least 6 characters"] }

Real-world example (ShopNest)

Creating an order is POST /api/orders → 201 with Location header. Fetching is GET /api/orders/{id} → 200 or 404.

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.