Query database

BookRepo

In controllers and services, we can inject DatabaseContext to call DB. However, that'd make the code difficult to test. Thus, it is common to add a respository or data access layer.

Add a folder Repos and add BookRepo.cs which implements IBookRepo interface and injects DatabaseContext.

public interface IBookRepo
{
    Task<long> Create(Book book);
}

public class BookRepo : IBookRepo
{
    private readonly DatabaseContext _context;

    public BookRepo(DatabaseContext context)
    {
        _context = context;
    }

    public async Task<long> Create(Book book)
    {
        await _context.Bookings.AddAsync(book);
        await _context.SaveChangesAsync();
        return book.Id;
    }
}

In DependencyConfigurator.cs, add

public static void RegisterDependencies(this WebApplicationBuilder builder)
{
    RegisterRepos(builder); //register repos before services
    RegisterServices(builder);
}

private static void RegisterRepos(this WebApplicationBuilder builder)
{
    builder.Services.AddScoped<IBookRepo, BookRepo>();
}

In BookService.cs, inject IBookRepo

public class BookService : IBookService
{
    private readonly ILogger<BookService> _logger;
    private readonly IClock _clock;
    private readonly IBookRepo _bookRepo;

    public BookService(ILogger<BookService> logger, IClock clock, IBookRepo bookRepo) //inject IBookRepo
    {
        _logger = logger;
        _clock = clock;
        _bookRepo = bookRepo;
    }

    public async Task<int> All(CreateBookRequest request)
    {
        return await _bookRepo.All();
    }

    public async Task<int> Create(CreateBookRequest request)
    {
        if (request.PublicationYear < 1900 || request.PublicationYear > _clock.Now.Year)
        {
            throw new ValidationException("Publication Year must be between 1990 and 2025");
        }

        var id = await _bookRepo.Create(new BookModel());
        return id;
    }
}

Test the API.