I am trying to use dependency injection for a repository, which in Program.cs is registered as a service. However the repository keeps getting reinstanciated each time the controller is called.

I have a feeling i need to move this to something not in the controller, and/or actually use the IServiceProvider rarther than just declaring it. This would give it has some form of permanence, but i am not sure what/where/how to do this.

The repo is just a List<Book> with CRUD operations and does not sit over entity framework or another data framework/database. Mostly as im just trying to learn and get an example of a repo over a list with DI in MVC. Its entirely possible that im flogging a dead horse with my approach.

I dont get any errors when navigating through my pages. When i break through the code, the operations within the repo are called fine, and do what i expect them to do. Its just when i go to my page of “view all” or “add” the repo is reset because of its reinstanciation (i presume).

Other than whats below, program.cs has not been changed.

Program.Cs

// Add services to the container.
builder.Services.AddControllersWithViews();

builder.Services.AddScoped<IUserRepository, UserRepository>();
builder.Services.AddScoped<IBookRepository, BookRepository>();

var app = builder.Build();

BookRepository.cs

    public class BookRepository : IBookRepository
    {
        private List<Book> _books;

        public BookRepository()
        {
            _books = new List<Book>();
        }

        public List<Book> GetAllBooks()
        {
            return _books;
        }

        public Book GetBookByISBN(string ISBN)
        {
            Book book = _books.Find(x => x.ISBN == ISBN);
            return book;
        }

        public void CreateBook(Book book) 
        {
            _books.Add(book);
        }

        public void DeleteBook(Book book)
        {
            _books.Remove(book);
        }
    }

and the LibraryController.cs constructor

        public LibraryController(IServiceProvider serviceProvider)
        {
            if (serviceProvider == null)
            {
                throw new ArgumentNullException(nameof(serviceProvider));
            }

            _bookRepository = serviceProvider.GetService<IBookRepository>() ??
                throw new ArgumentNullException(nameof(_bookRepository));
        }