Should the repository layer return data-transfer-objects (DTO)?

Question

I have a repository layer that is responsible for my data-access, which is called by a service layer. The service layer returns DTOs which are serialized and sent over the w

Answer 1

Short answer: No.

Long answer: repository is responsible for turning persisted data back to entities (models) and vice versa.

Model is a business Model representing a business entity. DTO on the other hand - while looks like Model - is concerned with transfer of the object between various environment and in essence is a transient object. Usually mappers are responsible for turning model into DTO.