In ASP.NET Core MVC, services are classes responsible for implementing the core business logic of your application. They are designed to be reusable, self-contained, and independent of specific controllers or views. Services are the backbone of your application, handling tasks like data access, calculations, communication with external systems, and any other operations that involve the “how” of your application’s functionality.
Key Purposes of Services Encapsulation of Business Logic: Services provide a clean way to encapsulate complex operations and keep them separate from your presentation layer (controllers and views). Reusability: A single service can be used by multiple controllers, promoting DRY (Don’t Repeat Yourself) principles and making your code more maintainable. Testability: Services can be easily unit tested in isolation, allowing you to verify the correctness of your business logic without the overhead of running the entire application. Dependency Injection (DI): Services are typically registered in the DI container, making them easily accessible to controllers and other components within your application.
Typical Responsibilities of Services Data Access: Communicating with databases or other data sources to fetch, insert, update, or delete data. Business Rules: Implementing the rules that govern how your application behaves (e.g., validation, calculations, transformations). Integration: Interacting with external systems or APIs. Notifications: Sending emails, SMS messages, or other notifications. Logging: Recording events and errors for troubleshooting and analysis.
Code // CitiesService.cs (Service) namespace Services { public class CitiesService { private List<string> _cities;
// Constructor public CitiesService() { _cities = new List<string>() { “London”, “Paris”, “New York”, “Tokyo”, “Rome” }; }
public List<string> GetCities() { return _cities; } } }
// HomeController.cs (Controller) public class HomeController : Controller { private readonly CitiesService _citiesService;
// Constructor (injecting the service) public HomeController() { _citiesService = new CitiesService(); }
[Route(“/”)] public IActionResult Index() { List<string> cities = _citiesService.GetCities(); return View(cities); // Pass the data to the view } }
Note that in this code example, there is no dependency injection being used. In real-world projects, it’s good practice to register your services with ASP.NET Core’s built-in dependency injection container and then have them injected into your controllers (or other components) through the constructor.
Explanation CitiesService Class: This class represents a simple service that holds a list of city names and provides a GetCities method to retrieve them. HomeController Class: Dependency: It has a dependency on the CitiesService class. Instantiation: In this simplified example, the CitiesService object is created directly within the controller’s constructor. Action Method: The Index action method calls the GetCities method of the _citiesService to retrieve the list of cities and then passes this data to the view.
Best Practices Single Responsibility Principle (SRP): Design your services to have a single responsibility to keep them focused and maintainable. Dependency Injection: Use dependency injection to manage service lifetimes and dependencies, making your code loosely coupled and easier to test. Interface-Based Programming: Define interfaces for your services to create abstraction layers and facilitate testing with mocks. Clear Naming: Use descriptive names for your services and their methods to make your code self-documenting. Testing: Write unit tests for your services to ensure that your business logic works correctly in isolation.
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Controllers in Asp.net Core