Can't pass in interface to controller without throwing error

Question

I created a service class 'TeacherService' with an interface that I want to pass it into my controller's constructor, but when I try there is an error in one of the constructors

As soon as I type a comma into the constructors parameters it red unerlines

new TeacherRepository()

saying it can't resolve the constructor. Here is the code.

public class TeacherController : Controller
{
    private readonly ITeacherRepository teacherRepository;
    private  readonly ITeacherService teacherService;

    // If you are using Dependency Injection, you can delete the following constructor
    public TeacherController() : this(new TeacherRepository())
    {
    }

    public TeacherController(ITeacherRepository teacherRepository, ITeacherService teacherService)
    {
        this.teacherRepository = teacherRepository;
        this.teacherService = teacherService;
    }

Answer 1

public TeacherController() : this(new TeacherRepository())

You are calling the second constructor that expects two parameters with just one. Add the default TeacherService for it to compile.