What is Clean Architecture: Part 9 - Setting Up the Application Project in Visual Studio

In our previous article, we discussed the design principles behind the Application Project, focusing on the importance of contracts, messaging, and the repository pattern. Now, it's time to put theory into practice by heading back to Visual Studio and starting the actual implementation.

Creating the Application Project

First things first—let’s create the Application Project that will house our core application logic. This project is a vital part of our architecture, as it encapsulates the business rules and interacts with the domain layer through well-defined contracts.

I've already set up a new class library in Visual Studio, named GloboTicket.TicketManagement.ApplicationProject. This project will contain all the necessary contracts and application logic that drive the functionality of our application.

Organizing the Application Project

Given the nature of our architecture, it's crucial to keep things organized right from the start. Even though our application isn't large, it's good practice to structure the project in a way that scales well for enterprise applications.

• Creating the Contracts Folder To maintain a clear separation of concerns, we’ll begin by creating a folder named Contracts. This folder will hold all the interfaces that define the operations our application will perform.

• Adding Subfolders for Better Organization Inside the Contracts folder, we'll add subfolders to categorize the different types of contracts. For instance, a Persistence folder will be created to store contracts related to database interactions. This way, we ensure that even as our project grows, the structure remains clean and navigable.

Introducing the IAsyncRepository Interface

One of the first contracts we’ll create is the IAsyncRepository interface. This interface will serve as a base repository contract that defines the essential CRUD operations.

if want to know more about repository pattern read this article
repository-pattern

public interface IAsyncRepository<T> where T : class
{
    Task<T> GetByIdAsync(Guid id);
    Task<IReadOnlyList<T>> ListAllAsync();
    Task<T> AddAsync(T entity);
    Task UpdateAsync(T entity);
    Task DeleteAsync(T entity);
}

• Generic Repository
  The IAsyncRepository interface is generic, meaning it can work with any entity type that is a class. This design allows us to create a single, reusable interface for all our repositories, ensuring consistency across the application.

• Key Methods
  The methods defined in IAsyncRepository include GetByIdAsync, ListAllAsync, AddAsync, UpdateAsync, and DeleteAsync. These methods cover the basic operations required for most entities in the application.

Creating Specific Repositories

While the generic IAsyncRepository provides a good starting point, we often need more specialized repositories tailored to specific entities. For example, we’ll create interfaces for managing events, orders, and categories.

• IEventRepository Interface

  public interface IEventRepository : IAsyncRepository<Event>
  {
      // Define additional methods specific to the Event entity
  }

• IOrderRepository Interface

  public interface IOrderRepository : IAsyncRepository<Order>
  {
      // Define additional methods specific to the Order entity
  }

• ICategoryRepository Interface

  public interface ICategoryRepository : IAsyncRepository<Category>
  {
      // Define additional methods specific to the Category entity
  }

Each of these interfaces extends IAsyncRepository and adds any methods that are unique to the respective entity. For example, IEventRepository might include methods for retrieving events within a certain date range.

Referencing the Domain Project

To make these specific repositories functional, we need to reference the domain entities in our application project. This involves adding a reference from the ApplicationProject to the DomainProject in Visual Studio. Once the reference is added, we can bring in the necessary domain models (like Event, Order, and Category) using the correct using statements.

Preparing for the Next Steps

With these contracts in place, we’ve laid the groundwork for our application logic. We’ll be writing most of our business logic against these contracts, ensuring that the core application remains decoupled from implementation details.

In the upcoming module, we’ll shift our focus to the implementation phase. Specifically, we’ll implement these repositories in the persistence layer and connect them to our database. This will bring our application closer to a functional state, where business rules are executed seamlessly through a well-defined architecture.

Conclusion

Setting up the Application Project is a crucial step in our clean architecture journey. By creating and organizing contracts, we’ve ensured that our application logic will be both scalable and maintainable. The next steps will involve implementing these contracts in the infrastructure, where the real power of our architecture will come to life. Stay tuned as we continue building this robust and clean architecture in the following articles!

For the complete source code, you can visit the GitHub repository: https://github.com/mohamedtayel1980/clean-architecture