c# - Constructor Dependency injection in asp.net core 2

I have read this official documentation: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/dependency-injection.

There is something i do not understand in constructor injection:

Let's have a look to my code, which works fine:

public class HomeController : Controller
{
    private readonly UserManager _userManager;
    private readonly SignInManager _signInManager;
    private readonly RoleManager _roleManager;

    public HomeController(
        SignInManager signInManager,
        UserManager userManager,

        RoleManager roleManager)
    {
        _userManager = userManager;
        _signInManager = signInManager;
        _roleManager = roleManager;
    }

It works fine too if change constructor parameter orders or if i remove some parameters like this:

public class HomeController : Controller
{
    private readonly UserManager _userManager;
    private readonly SignInManager _signInManager;

    public HomeController(
        UserManager userManager
        SignInManager signInManager,
        )
    {

        _userManager = userManager;
        _signInManager = signInManager;
    }

I have understood the concept of DI. What i do not understand is how does it works in C# to have something dynamic in constructor parameters ?
Is there a set of all kind of overload constructors ?

Thanks

Answer

how does it work in C# to have something dynamic in constructor parameters ? Is there a set of all kind of overload constructors?

Don't use "dynamic" like that, it's a buzzword in that sentence. In programming, everything is dynamic.

If you mean to ask how a DI framework can match up registered services with constructor parameters, then yes, there is a set of constructor overloads.

The DI framework finds these through reflection, see MSDN: Type.GetConstructors(). Then for each constructor, the framework obtains the parameters of each constructor, matches those up with the registered services and invokes one of the constructors.