Onion Architecture: A Guide to Clean and Sustainable Code

In the Application Layer, Create a New Folder called Features. This will have all the logic related to each Feature / Entity. Under this folder, add a new one and name it ProductFeatures. We will implement the Mediator pattern later in this tutorial. Tip #2 – While running the application, you would see that it navigated to ../weatherforecast by default. In the WebApi Project, Properties drill down, you can find a launchsettings.json file.

All layers must also supply information that inner layers can easily consume. The objective is to enhance coupling inside a vertical slice across layers while minimizing coupling across layers. The outer circle’s classes, methods, variables, and source code generally depend on the inner circle but not the other way around. The fundamental rule is that all code can depend on layers more central, but code cannot depend on layers further out from the core. This architecture is unashamedly biased toward object-oriented programming, and it puts objects before all others.

What makes Onion Architecture so popular among techies?

We will explain why this is important in the next section. The modular design facilitates the introduction of new technologies or frameworks without affecting the core business logic, enhancing the scalability and future-proofing of the application. Domain-driven design (DDD) is an approach to developing software for complex needs by deeply connecting the implementation to an evolving model of the core business concepts. An Anemic Domain Model is a domain model that has no behavior, just data. It acts just like a bag of data, while the behavior itself is implemented in a service. This architecture should be used when creating services that deal with business rules.

We will build a RESTful API that follows the Onion architecture, with ASP.NET Core and .NET 5. Onion architecture uses the concept of the layer but is different from N-layer architecture and 3-Tier architecture. When working with Scrum, you will probably want to break the development of the software into different tasks, so it can be done by different people.

Hexagonal Architecture Why, What, and How…

The city center contains many remains of ancient Serdica that have been excavated and are on public display, including Complex Ancient Serdica, eastern gate, western gate, city walls, thermal baths, 4th c. Church of St. George Rotunda, amphitheatre of Serdica, the tombs and basilicas under the basilica of St. Sophia. Nineteenth-century drawings show that the decoration of the Hagia Sophia also included comprehensive series of saints. Of these saints, which stood in rows on the nave walls above the galleries, only a few have survived. According to the drawings, those of the middle zone represented prophets and those of the lower depicted holy bishops. Higher up there may have been a guard of angels and, in the centre of the cupola, probably a mosaic of Christ.

In the Service layer, we are going to depend only on the interfaces that are defined by the layer below, which is the Domain layer. We can write business logic without concern about any of the implementation details. If we need anything from an external system or service, we can just create an interface for it and consume it. The higher layers of the Onion will take care of implementing that interface transparently. Application services also referred to as “Use Cases”, are services responsible for just orchestrating steps for requests and should not have any business logic.

Build Microservices with .NET Core and RabbitMQ (Step-by-Step)

There are different boulevards and streets in the city with a higher amount of traffic than others. The extension of the underground system is hoped to alleviate the city’s immense traffic problems. Arena Sofia holds many indoor events and has a capacity of up to 19,000 people depending on its use. The venue was inaugurated on 30 July 2011, and the first event it hosted was a friendly volleyball match between Bulgaria and Serbia. There are more than fifteen swimming complexes in the city, most of them outdoor.[162] Nearly all of these were constructed as competition venues and therefore have seating facilities for several hundred people. Sofia concentrates the majority of Bulgaria’s leading performing arts troupes.

Since this is a very basic controller that calls the mediator object, I will not go in deep. However, I have previously written a detailed onion architecture article on CQRS implementation in ASP.NET Core 3.1 API. You could go through that article which covers the same scenario.

Layers of Onion architecture

They are going to be treated the same as if they were defined conventionally. We are creating a project called Presentation and giving it a reference to the Microsoft.AspNetCore.Mvc.Core NuGet package so that it has access to the ControllerBase class. To learn how to implement the repository pattern with Entity Framework Core you can check out this article ASP.NET Core Web API – Repository Pattern. With this approach, we are being very explicit about what the higher layers of the Onion can and can not do. It is easy to miss here that the Services.Abstractions project does not have a reference to the Domain project. The entities defined in the Domain layer are going to capture the information that is important for describing the problem domain.

On the contrary, if some functionalities were tightly connected, we had to combine microservices into one. And the most challenging task was to find a balance between all these functions. Our customer needed a software system compatible with their hardware so that clients could buy equipment, install software and create and manage content. The challenge was to create a cloud software solution for a digital signage hardware manufacturer.

Domain Services

This renowned poet, philosopher and mystic helped spread the Sufi branch of Islam throughout the Turkic-speaking world. Following Yasawi’s death in 1166, his resting placed served as sacred ground for Sufi Silk Road travellers. Here, Meldekhanov reveals five places you must visit to better understand the city’s art, cuisine, entertainment, architecture and culture.

• All of the layers interact with each other strictly through the interfaces defined in the layers below.
• This architecture provides us a better way to build applications using this architecture our applications are better testable, maintainable, and dependable on infrastructures like databases and services.
• The pattern entails constructing concentric circles or layers around a central domain model, each of which is responsible for a distinct task and has dependencies flowing inward toward the core.
• This will be an Empty API Controller which will have API Versioning enabled in the Attribute and also a MediatR object.
• With the CRUD logic out of the way, let’s set up EFCore in the Persistence Layer and try to generate a database.

ContainerNinja is a boilerplate template project to demonstrate building a multi-container Full Stack application with ASP.NET Core (.NET 6) Web API following Clean Architecture, and Angular. The great thing about this approach is that the migrations will be automatically applied when we create new migrations, further down the road. To learn more about migrations and how to seed data with EF Core in both .NET 5 and .NET 6 check out this article Migrations and Seed Data with Entity Framework Core. However, since the Web application and the database server will be running inside of containers, how are we going to create the actual database for the application to use?

Taking Care of Database Migrations

RiderFareCalculator is implemented in this layer also, and it depends on the fare repository and route service interfaces declared in the same layer. Note that with this approach, we do not depend on the external service, rather the external service depends on our declared contracts. Onion Architecture has great practical value, particularly for creating expansive, intricate software systems. It is simpler to test, maintain, and upgrade the codebase over time when an application is built in layers, which isolates the business logic from the display layer and infrastructure.