ASP.NET Core Web API Interview Question #33

Should create, update, and response DTOs be the same class?

DTOs, Model Binding, Validation & API Responses Junior Beginner

Quick Interview Answer

They can be the same for very simple contracts, but separate DTOs are usually clearer when the operations have different requirements. A create request may require fields that an update does not, while a response may contain server-generated identifiers and timestamps that clients must not submit.

Detailed Explanation

Purpose-specific DTOs improve validation, security, documentation, and long-term API evolution.

Code Example

public sealed class CreateProductRequest { /* client input */ }
public sealed class UpdateProductRequest { /* editable fields */ }
public sealed class ProductResponse     { /* public output */ }