ApiEfCoreLibrary/ApiEfCoreLibrary/Endpoints/Book/GetBookEndpoint.cs

using ApiEfCoreLibrary.DTO.Book.Response;
using FastEndpoints;
using Microsoft.EntityFrameworkCore;

namespace ApiEfCoreLibrary.Endpoints.Book;

public class GetBookRequest
{
    public int Id { get; set; }
}

public class GetBookEndpoint(LibraryDbContext database) : Endpoint<GetBookRequest, GetBookDto>
{
    public override void Configure()
    {
        Get("/api/books/{@Id}", x => new {x.Id});
        AllowAnonymous();
    }

    public override async Task HandleAsync(GetBookRequest req, CancellationToken ct)
    {
        var book = await database.Books.Include(b => b.Author).SingleOrDefaultAsync(x => x.Id == req.Id, ct);

        if (book == null)
        {
            await Send.NotFoundAsync(ct);
            return;
        }
        
        GetBookDto responseDto = new()
        {
            Id = book.Id,
            Title = book.Title,
            BookAuthorId = book.AuthorId,
            BookAuthorName = book.Author.Name,
            BookAuthorFirstName = book.Author.FirstName,
            ReleaseYear = book.ReleaseYear,
            Isbn = book.Isbn
        };
        
        await Send.OkAsync(responseDto, ct);
    }
}