ASP — ASP.NET Dependency Injection

Register Services

builder.Services.AddScoped<IUserService, UserService>();
builder.Services.AddSingleton<ICacheService, CacheService>();
builder.Services.AddTransient<IEmailService, EmailService>();

Service Lifetimes

Lifetime	Description
Transient	New instance each request
Scoped	Once per request
Singleton	One instance forever

Service Interface

public interface IUserService
{
    User GetById(int id);
    IEnumerable<User> GetAll();
}

public class UserService : IUserService
{
    private readonly AppDbContext _context;
    
    public UserService(AppDbContext context)
    {
        _context = context;
    }
    
    public User GetById(int id) => _context.Users.Find(id);
    public IEnumerable<User> GetAll() => _context.Users.ToList();
}

Inject in Controller

[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
    private readonly IUserService _userService;
    
    public UsersController(IUserService userService)
    {
        _userService = userService;
    }
    
    [HttpGet]
    public IActionResult GetAll()
    {
        return Ok(_userService.GetAll());
    }
}

Mini Practice

1. Create service interface
2. Implement service
3. Register service
4. Inject in controller

Up Next

Continue with ASP.NET Configuration — configuration.