Question

I read a bout IDependencyResolver in MVC (fundamentalbook), but i don’t know what is exactly DependencyResolver in mvc?

Could some one please explain these methods?

Answer 1

It allows for implementing dependency injection into controllers and other components. Brad Wilson wrote a nice article about it. For example when you implement a custom dependency resolver that is capable of returning proper implementations for a give type you could have your ASP.NET MVC controllers take abstract dependencies or interfaces as constructor arguments:

public class HomeController: Controller
{
    private readonly ISomeService _someService;
    public class HomeController(ISomeService someService)
    {
        _someService = someService;
    }

    ... some actions
}

if you have written a custom dependency resolve it will be able to inject the proper implementation of the interface when instantiating the controller.

Dependency Injection allows for weaker coupling between the different layers of your application and making them easier to unit test in isolation.