What is Onion Architecture?

Jeffrey Palermo coined the Onion Architecture term in 2008

This architecture provides a better way to build applications for better testability, maintainability and dependability on the infrastructures like databases and services

What are the Advantages of Onion Architecture?

• It provides better maintainability as all the codes depend on layers or the centre.
• It provides better testability as the unit test can be created for separate layers without an effect on other modules of the application.
• It develops a loosely coupled application as the outer layer of the application always communicates with the inner layer via interfaces.
• Any concrete implantation would be provided to the application at run time
• Domain entities are the core and centre part. It can have access to both the database and UI layers
• The internal layers never depend on the external layer. The code that may have changed should be part of an outer layer.