What are the reasons for defining the CatalogRepository class in the Infrastructure layer instead of the Application layer?

The CatalogRepository class is responsible for data access, such as to a database or external services. In a layered architecture, the Infrastructure layer is intended for implementing technical details, such as working with databases, file systems, and network requests.

Defining CatalogRepository in the Infrastructure layer is justified because:

• It encapsulates the details of storing and retrieving data, which should not affect business logic.
• The Application layer contains business logic and interfaces, not specific implementations of data access.
• This allows easy changing of the data access implementation without modifying business logic.

Example:

// In the Application layer
public interface ICatalogRepository
{
    Catalog GetCatalogById(int id);
}

// In the Infrastructure layer
public class CatalogRepository : ICatalogRepository
{
    public Catalog GetCatalogById(int id)
    {
        // Implementation of database access
    }
}