Dependency Injection (DI) & Service Lifetimes

Understanding Transient, Scoped, and Singleton IoC container lifetimes

« The Middleware Pipeline & Request Lifecycle« Previous Controller-Based Web APIs & Routing »Next »

ASP.NET Core includes a built-in Inversion of Control (IoC) container that manages object creation and dependency resolution throughout the application lifecycle.

The Three Service Lifetimes

Transient (AddTransient): Created each time they are requested. Ideal for lightweight, stateless services.

Scoped (AddScoped): Created once per client HTTP request connection. The standard lifetime for Entity Framework DbContext and business repositories.

Singleton (AddSingleton): Created once upon initial request (or application startup) and shared by every subsequent request throughout the application lifetime. Ideal for caching or telemetry clients.

Registering and Injecting Services

Try It Yourself »

// 1. Interface and Implementation
public interface ICourseCatalogService
{
    IEnumerable<string> GetFeaturedCourses();
}

public class CourseCatalogService : ICourseCatalogService
{
    public IEnumerable<string> GetFeaturedCourses() => 
        new[] { "Cloud Native .NET 8", "Kubernetes Microservices", "C# Deep Dive" };
}

// 2. Register in Program.cs
builder.Services.AddScoped<ICourseCatalogService, CourseCatalogService>();

// 3. Inject into a Controller or Minimal API via constructor
[ApiController]
[Route("api/[controller]")]
public class CoursesController : ControllerBase
{
    private readonly ICourseCatalogService _catalogService;

    public CoursesController(ICourseCatalogService catalogService)
    {
        _catalogService = catalogService;
    }

    [HttpGet("featured")]
    public IActionResult GetFeatured() => Ok(_catalogService.GetFeaturedCourses());
}

Constructor injection ensures loose coupling and makes components effortless to unit test with mocks.

Lifetime	Registration Method	Instance Frequency
Transient	AddTransient<T>()	New instance every single time requested
Scoped	AddScoped<T>()	Single instance per HTTP client request
Singleton	AddSingleton<T>()	One shared instance for the entire server process

Google AdSense Slot (inContentBanner)

Set your Publisher ID in src/config/ads.ts to display live ads.

Test Yourself With Exercise

+15 XP

Which service lifetime creates a single instance per client HTTP request, making it ideal for DbContext database sessions?

« Previous: The Middleware Pipeline & Request Lifecycle Next: Controller-Based Web APIs & Routing »