在MVC中没有为此对象错误定义无参数构造函数

Question

I want to use Dependency Injection on AccountController but i am getting this error "No parameterless constructor defined for this object" when login.Is this a true approach that using Dependency Injection while loginig.A lot of person use this approach on login control.

public interface IAuthProvider {
    bool Authenticate(string username, string password);
}

public class AccountController : Controller {
    IAuthProvider authProvider;

    public AccountController(IAuthProvider auth) {
        authProvider = auth;
    }

    public ViewResult Login() {
        return View();
    }

    [HttpPost]
    public ActionResult Login(LoginViewModel model, string returnUrl) {

        if (ModelState.IsValid) {
            if (authProvider.Authenticate(model.UserName, model.Password)) {
                return Redirect(returnUrl ?? Url.Action("Index", "Admin"));
            } else {
                ModelState.AddModelError("", "Incorrect username or password");
                return View();
            }
        } else {
            return View();
        }
    }
}

Answer 1

I'm guessing that you're using Unity. If so, you don't need a parameterless constructor. When registering your instance you should use an InjectionConstructor . With that Unity can resolve the correct constructor.