Dependency injection

ASP.NET Core instantiates the controllers through its built-in DI framework. Since it fully supports constructor injection, you can have any registered services injected as parameters to your constructor:

//ConfigureServices
services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

//HomeController
public HomeController(IHttpContextAccessor accessor) { ... }

However, you can also request a service from the DI in a service locator way by leveraging the HttpContext.RequestServices property as follows:

var accessor = this.HttpContext.RequestServices.GetService<IHttpContextAccessor>();

In action methods, you can also inject a service by decorating its typed parameter with the [FromServices] attribute, as follows:

public IActionResult Index([FromServices] IHttpContextAccessor accessor) { ... }

The next topic covers a very important topic, especially for those that wish to implement multilingual sites.