Unfolding infrastructure in the Onion architecture Dani Jug Blog.

The Service layer holds interfaces with common operations, such as Add, Save, Edit, and Delete. Also, this layer is used to communicate between the UI layer and repository layer. The Service layer also could hold business logic for an entity. In this layer, service interfaces are kept separate from its implementation, keeping loose coupling and separation of concerns in mind. The biggest offender is the coupling of the UI and business logic to the data access.

Adding facades are really the first step in building an onion architecture out of an n-layered architecture. The first layer around the Domain Model is typically where we would find interfaces that provide object saving and retrieving behavior, called Repository Interfaces. The main premise of this architecture is that it controls coupling. The number of levels may differ, but the center is always the Domain Model, that is, those model classes that are used in the application and whose objects are stored in the database. The main problem with this architecture is that all layers are built on top of the Data Access Layer and are, in fact, tied to a certain type of data storage. Based on the DDD model, we’ve created onion architecture (aka hexagonal or clean architecture).

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ASP.NET Core offers Health Checks Middleware and libraries for reporting the health of app infrastructure components. At times, we had to move a particular functionality into a separate microservice if it appeared in many places in the system. 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.

In the custom service folder, we will create the custom service class that inherits the ICustomService interface code of the custom service class is given below. Now our service layer contains the reference of the repository layer. But here we need to add the project reference of the Domain layer in the repository layer. Write click on the project and then click the Add button after that we will add the project references in the Repository layer. Add the Data in the domain that is used to add the database context class. The database context class is used to maintain the session with the underlying database using which you can perform the CRUD operation.

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In this architecture, the Presentation Layer generally holds the part that the User can collaborate with, i.e, WebApi, MVC, Webforms, etc. Business Logic is likely the main piece of this whole arrangement. It holds all the rationale connected with the Business prerequisites. Presently, every application in a perfect world has its own committed Database. This layer normally holds ORMs for ASP.NET to read or write to a database.

• One outer layer which may surprise many is Infrastructure.
• Among the characteristics, neck thickness contributed the maximum to the diversity followed by Total Soluble Solids (TSS).
• In the Build Tab enable the XML Documentation file and give an appropriate file name and location.
• And personally I would use them together for every application I need to be scalable, maintainable, highly covered by tests, evolvable and understandable.
• If a process or domain layer couples itself with infrastructure concerns, it is doing too much and becomes difficult to test.

For example, let’s say you are developing a banking system. Then, you are implementing a use case which lets the user check her or his account balance. Below is the list of criteria I use to move the functional to the CoreUtils project/folder. Passionate about travel, languages and cultural diversity exploration. I highly recommend you to read the article from Jeffrey Palermo about Onion Architecture.

Use Interfaces and Contracts:

If we apply the principles of the Onion Architecture to the layered architecture, we need to turn the layer diagram upside down. Upon first sight the layer model seems straightforward and easy to adopt. Unfortunately developers often take the layering literally. Individual layer implementations can be replaced by semantically equivalent implementations without too great of an effort. At its core, Clean Architecture is a way of organizing a software system
in a way that separates the concerns of the various components,
making it easier to understand and maintain.

In the Services.Abstractions project you can find the definitions for the service interfaces that are going to encapsulate the main business logic. Also, we are using the Contracts project to define the Data Transfer Objects (DTO) that we are going to consume with the service interfaces. An Anemic Domain Model is a domain model that has no behavior, just data.

Implementing Onion Architecture in ASP.NET Core WebApi Project

In this article, we will see Onion architecture in detail. The very centre of the Model, this layer can have dependencies only on itself. It represents the Entities of the Business and the Behaviour of these Entities. Each layer bounds together concepts that will have a similar rate of change. Code should depend only on the same layer or layers more central to itself. Connect and share knowledge within a single location that is structured and easy to search.

We can use lower layers of the Onion architecture to define contracts or interfaces. The outer layers of the architecture implement these interfaces. This means that in the Domain layer, we are not concerning ourselves with infrastructure details such as the database or external services. The domain models and services will be onion architecture software inside this layer, containing all the business rules of the software. It should be purely logical, not performing any IO operations at all. As per traditional architecture, the UI layer interacts to business logic, and business logic talks to the data layer, and all the layers are mixed up and depend heavily on each other.

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It is simpler to test and maintain if the domain logic is kept apart from the other levels. Because modifications to one layer don’t affect the others, this separation of responsibilities makes code maintenance and updating simpler over time. Building clean and durable code is critical for any project’s long-term success in software development. The difference between clean and sustainable code is that the former can be updated and maintained throughout time, while the latter is simple to read, comprehend, and edit. The presentation layer is the default Asp.net core web API project Now we need to add the project references of all the layers as we did before.

The interesting part with the ServiceManager implementation is that we are leveraging the power of the Lazy class to ensure the lazy initialization of our services. This means that our service instances are only going to be created when we access them for the first time, and not before that. 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.

Domain Entities and Business Logic:

Therefore what we do is that we create interfaces in the Application Layer and these interfaces get implemented in the external layers. This is also known as DIP or Dependency Inversion Principle. 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. However, in the OnModelCreating method, we are configuring our database context based on the entity configurations from the same assembly. As you can see, we mark the service implementations with the internal keyword, which means they will not be publicly available outside of the Services project.