Building a web application that's both robust and easy to maintain requires a solid architectural foundation. Enter the Three-Layer Architecture, a framework that enhances the structure and scalability of web projects. In this article, we'll explore how to implement this architecture in ASP.NET Core, a versatile platform for creating modern web applications.
The Three-Layer Architecture, also known as n-tier architecture, divides an application into three main layers: presentation, business logic, and data access. Each layer has a specific role, making the codebase modular and organized. This approach simplifies development, making it easier to understand and extend the application.
Join us as we break down the key components and their roles, providing insights into how this architecture can benefit your web development endeavors.
Table of Contents:
3. Code Example
5. Conclusion
Three-Layer Architecture in ASP.NET Core
A three-layer architecture in ASP.NET Core typically consists of the following layers:
Presentation Layer: This is the top layer that deals with user interface and user interaction. It's responsible for handling user requests, rendering views, and presenting data to the user. In ASP.NET Core, this layer often includes controllers, views, and client-side code.
Application or Business Logic Layer: This layer contains the application's core business logic. It processes requests from the presentation layer, communicates with the data access layer, and orchestrates the overall application behavior. It often includes services, application logic, and business rules.
Data Access Layer: This layer is responsible for interacting with the data storage, which could be a database, file system, or external services. It includes database access code, data models, and data repositories.
Here's a simple example of a three-layer architecture in an ASP.NET Core application using a fictional task management system:
Presentation Layer (Web Application):
Controllers: Handle HTTP requests, interact with the application layer, and return views or JSON responses.
Views: Display data to users and capture user input.
View Models: Act as a bridge between the views and controllers, shaping the data for presentation.
Application Layer:
Services: Contain the core business logic for managing tasks, users, and other application-specific functionality.
Models: Define the data structures for tasks, users, and other entities.
DTOs (Data Transfer Objects): Represent data transferred between the presentation layer and application layer.
Data Access Layer:
Repositories: Provide data access methods for storing and retrieving tasks and user data.
Database Context: Define the database schema and handle database connections.
Entity Framework (or other ORM): Interact with the database using an Object-Relational Mapping (ORM) framework.
Also Read: Tools to build ASP.NET Blazor Apps
NuGet Packages
The necessary NuGet packages for the provided example would include:
ASP.NET Core Packages:
Microsoft.AspNetCore.Mvc
Microsoft.Extensions.DependencyInjection
Entity Framework Core Packages:
Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.SqlServer (or another database provider of your choice)
Here's a simplified list of the packages you might need in your project file (.csproj):
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
<OutputType>Exe</OutputType><TargetFramework>netcoreapp3.1</TargetFramework>
</PropertyGroup><ItemGroup><PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.2.0" />
<PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="2.2.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.0" />
</ItemGroup>
</Project>Make sure to check for the latest versions of these packages on the NuGet Package Manager or the official NuGet website as versions may have changed since my last training data in January 2022.
To install these packages, you can use the Package Manager Console or the NuGet Package Manager in Visual Studio, or add the necessary XML elements directly to your .csproj file and let the IDE restore the packages.
Example of Three-Layer Architecture in Asp.Net Core
// Presentation Layer (Web Application)
public class TaskController : Controller
{
private readonly ITaskService _taskService;
public TaskController(ITaskService taskService)
{
_taskService = taskService;
}
public IActionResult Index()
{
var tasks = _taskService.GetTasks();
return View(tasks);
}
}
// Application Layer
public interface ITaskService
{
IEnumerable<TaskDto> GetTasks();
}
public class TaskService : ITaskService
{
private readonly ITaskRepository _taskRepository;
public TaskService(ITaskRepository taskRepository)
{
_taskRepository = taskRepository;
}
public IEnumerable<TaskDto> GetTasks()
{
var tasks = _taskRepository.GetTasks();
return tasks.Select(task => new TaskDto
{
Id = task.Id,
Title = task.Title,
// Map other properties as needed
});
}
}
// Data Access Layer
public interface ITaskRepository
{
IEnumerable<Task> GetTasks();
}
public class TaskRepository : ITaskRepository
{
private readonly AppDbContext _context;
public TaskRepository(AppDbContext context)
{
_context = context;
}
public IEnumerable<Task> GetTasks()
{
return _context.Tasks.ToList();
}
}
// Data Transfer Object (DTO)
public class TaskDto
{
public int Id { get; set; }
public string Title { get; set; }
// Add other properties as needed
}
// Entity (Assuming Entity Framework)
public class Task
{
public int Id { get; set; }
public string Title { get; set; }
// Add other properties as needed
}
// Database Context (Assuming Entity Framework)
public class AppDbContext : DbContext
{
public DbSet<Task> Tasks { get; set; }
public AppDbContext(DbContextOptions<AppDbContext> options)
: base(options)
{
}
}In the above code:
Presentation Layer (Web Application)
TaskController
This class is part of the presentation layer and is responsible for handling HTTP requests and interacting with the user interface.
It depends on the ITaskService interface to retrieve tasks.
Application Layer
ITaskService
An interface defining the contract for a service that deals with tasks. It has a method GetTasks() to retrieve tasks.
TaskService
Implements the ITaskService interface.
Depends on the ITaskRepository interface to retrieve tasks from the data access layer (repository).
Maps the retrieved Task entities to TaskDto objects, providing a level of abstraction between the data access layer and the presentation layer.
Data Access Layer
ITaskRepository
An interface defining the contract for a repository responsible for retrieving tasks.
It has a method GetTasks() to retrieve a collection of tasks.
TaskRepository
Implements the ITaskRepository interface.
Depends on the AppDbContext class, which is an Entity Framework database context.
Retrieves tasks from the database using Entity Framework.
Data Transfer Object (DTO)
TaskDto
A data transfer object (DTO) represents a simplified version of a task.
It is used to transfer data between layers without exposing the internal details of the Task entity.
Entity
Task
Represents the entity that corresponds to the tasks stored in the database.
It has properties such as Id and Title.
Database Context
AppDbContext
A class representing the Entity Framework database context.
Includes a DbSet<Task> property to represent the tasks table in the database.
Configured to work with Entity Framework through dependency injection.
Additional Notes:
Dependency Injection: The code follows the dependency injection principle, where dependencies are injected into the constructor rather than being directly instantiated. This makes it easier to replace implementations or mock dependencies during testing.
Separation of Concerns: The code adheres to the separation of concerns principle by dividing the application into layers, each with its own responsibility. The presentation layer handles user interactions, the application layer contains business logic, and the data access layer deals with database interactions.
DTO (Data Transfer Object): The use of DTO (TaskDto) helps in transferring data between layers without exposing the internal details of the entities, promoting a cleaner separation between layers.
Entity Framework: Assumes the use of Entity Framework for data access, but you can replace it with other data access technologies if needed.
Interfaces: Interfaces (ITaskService and ITaskRepository) are used to define contracts, providing a level of abstraction and making it easier to substitute implementations.
Benefits of using Three-Layered Architecture in ASP.NET Core
Three-layer architecture is commonly used in ASP.NET Core to structure web applications in a way that enhances maintainability and scalability.
Let's understand in detail:
Maintainability:
Scenario: Imagine you're developing an e-commerce website with ASP.NET Core. You have components responsible for handling user interactions (presentation layer), processing orders, applying business rules (business logic layer), and storing/retrieving data from a database (data access layer).
How Three-Layer Architecture Enhances Maintainability:
If you need to update the way orders are processed (e.g., adding a new discount rule), you would primarily modify the business logic layer. This separation allows you to focus on the specific functionality without affecting the rest of the application.
Changes to the database schema or the way data is stored/retrieved would be confined to the data access layer, minimizing the impact on other parts of the application.
This separation of concerns makes the codebase more modular and easier to maintain because each layer has a distinct responsibility.
Scalability:
Scenario: As your e-commerce site gains popularity, you may encounter increased traffic. Scalability becomes crucial to handle more users and transactions.
How Three-Layer Architecture Enhances Scalability:
If the increase in traffic requires scaling the data access layer (e.g., optimizing database queries or switching to a more scalable database system), you can focus on improving that layer without affecting how the business logic or presentation layers operate.
Similarly, if there's a need to scale the user interface to handle more concurrent users, optimizations can be made in the presentation layer independently.
The modular structure allows for targeted improvements in the areas needing scale, making the application more adaptable to growth.
Conclusion
The Three-Layer Architecture proves to be a fundamental and beneficial approach in ASP.NET Core web development. By organizing applications into presentation, business logic, and data access layers, this architecture enhances maintainability and scalability.
The clear separation of concerns facilitates easier modifications and updates to specific parts of the application without affecting the whole system. ASP.NET Core seamlessly accommodates this structure, with controllers managing user interactions, services handling business logic, and data access components managing data persistence.
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