Because the patterns are so similar, it’s hard to choose one. So far, things are looking very similar between the two architectural patterns. People often use the topics interchangeably for this reason. Notably, the outermost layers only depend on the inner layers, not the other way around. As we gradually ‘peel the layers of the onion,’ we expose the inner layers.
We have our domain or business entities, our exceptions, our repository interfaces, and our service interfaces/implementations. Additionally, these components are integral to the architecture. Notice everything is onion architecture .net core generic around “Pizza” and “Orders”. The second layer of the onion contains the Application Interfaces. The contracts defined here orchestrate the use of the Domain Services and are the entry point for all business logic.
Implementing Onion Architecture in ASP.NET Core WebApi Project
In order to access the Database, we introduce a Data Access Layer. This layer usually holds ORMs for ASP.NET to fetch/write to the database. There are more examples, but hopefully, you get the idea.
Onion vs Layered Architecture
The purpose of the Presentation layer is to represent the entry point to our system so that consumers can interact with the data. We can implement this layer in many ways, for example creating a REST API, gRPC, etc. 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. These exceptions will be handled by the higher layers of our architecture.
Next, we’ll create abstractions in the OnionArchitectureGuide.Application.Abstraction before implementing these contracts in the OnionArchitectureGuide.Application.Implementation. In the next post, we’ll start implementing Onion Architecture layer by layer. Let’s take a deeper look into the “Core” layers in each, to try and analyze the logical architecture and project structure.
All of the layers interact with each other strictly through the interfaces defined in the layers below. The flow of dependencies is towards the core of the Onion. We will explain why this is important in the next section. Onion Architecture is like giving your business logic its own safe room. Everything else works around it, but can’t mess with it. If you’re tired of fragile, messy code, this approach might just be what you need.
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- However the principles are essentially the same, so from here on out we’ll be focusing on onion.
- With the CRUD logic out of the way, let’s set up EFCore in the Persistence Layer and try to generate a database.
- The great thing about this approach is that the migrations will be automatically applied when we create new migrations, further down the road.
- The service layer holds all the business logic of the entity.
- It lets a specific team or individual work on a particular layer without disturbing the integrity of the others.
- Next, we looked at the Infrastructure layer, where the implementations of the repository interfaces are placed, as well as the EF database context.
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 article on CQRS implementation in ASP.NET Core 3.1 API. You could go through that article which covers the same scenario. With the CRUD logic out of the way, let’s set up EFCore in the Persistence Layer and try to generate a database. Install the following packages to the Persistence Project. To maintain structural Sanity in Mid to Larger Solutions, it is always recommended to follow some kind of architecture.
Now, let’s look at some of the custom exceptions that we have inside the Exceptions folder. These are just some of the examples of what we could define in the Domain layer. We can be more or less strict, depending on our needs. We have to realize that everything is a tradeoff in software engineering.
Migrating from Layered to Onion
We will start off by creating a Blank Solution on Visual Studio. PS, I use Visual Studio 2019 Comunity which is completely FREE. Domain and Application Layer will be at the center of the design. 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. Any small change in the Business Logics layer or Data access layer may prove dangerous to the integrity of the entire application.
- By adhering to Onion Architecture principles, you can build robust, scalable applications in .NET Core that are well-organized and easy to maintain over time.
- Domain and Application Layer will be at the center of the design.
- They represent a way to structure the code that clearly separates the domain of the problem from the underlying technologies that implement the solution.
- 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.
The obvious advantage of the Onion architecture is that our controller’s methods become very thin. We moved all of the important business logic into the Service layer. 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. Then we can create our controllers inside this project. We are using a Web API built with ASP.NET Core to create a set of RESTful API endpoints for modifying the domain entities and allowing consumers to get back the data.
Onion Architecture In ASP.NET Core 6 Web API
This project can save well over 200+ hours of development time for your team. Now, let’s work on the Core Layers starting from the Domain Project. It basically has the models/entities, Exception, validation rules, Settings, and anything that is quite common throughout the solution. You can see the clear separation of concerns as we have read earlier.
I really enjoyed how you broke down Onion Architecture in such a practical and approachable way. Your explanations about dependency direction and the importance of keeping business logic isolated from infrastructure are spot on. The code samples make it easy for anyone to see the benefits and the migration steps are super valuable, especially for teams moving away from traditional layered architectures. This implementation follows the Onion Architecture principles, keeping the core logic separated from infrastructure concerns. Adjustments and improvements can be made based on specific requirements and additional features.
And in the Startup class/ ConfigureServices method of the WebApi Just Add the following line. You can now see the advantage of this kind of approach. Now add a Product Class that inherits the Id from the BaseEntity. Create a new class Entities/Product.cs in the Domain Project. Here is a list of features and tech we will be using for this setup. The presentation layer is where you would Ideally want to put the Project that the User can Access.
