The Onion architecture, introduced by Jeffrey Palermo, overcomes the issues of the layered architecture with great ease. Any small change in the Business Logics layer or Data access layer may prove dangerous to the integrity of the entire application. In N Layer Architecture, the Database is usually the Core of the Entire Application, i.e It is the only layer that doesn’t have to depend on anything else. This would defeat the purpose of having a clean architecture, yeah? Is it really needed? In most of the cases the UI (presentation) layer would be coupled to the Data Access Layers as well. Thus, we would be creating a bunch of unnecessary couplings. To keep it clear, in the above diagram we can see that the presentation layer depends on the logics layer, which in turn depends on the data access and so on. This is something really bad in building scalable applications and may pose issues with the growth of the codebase. Instead of building a highly decoupled structure, we often end up with several layers that are depending on each other. In this article, we will deal with the Layered Architecture. In cases where there is both a physical and logical separation of concerns, it is often referred to as n-tiered application where n is the number of separations. When there is just a logical separation in your application, we can term it as layers or N Layers. You must have seen most of the Open Sourced Projects having multiple layers of Projects within a complex folder structure. To maintain structural Sanity in Mid to Larger Solutions, it is always recommended to follow some kind of architecture. Summary The Need to Follow an Architecture.Clean Architecture with ASP.NET Core WebApi – Template.Advantages of Onion Architecture in ASP.NET Core.Generate the Migrations and the Database.Setting Up EF Core on the Persistence Project.Implementing MediatR for CRUD Operations.Adding the Required Interfaces And Packages in Application Layer.Adding The Entities to the Domain Project.Implementing Onion Architecture in ASP.NET Core WebApi Project.Getting Started with Onion Architecture.

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