Libation/DataLayer/QueryObjects/BookQueries.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using Microsoft.EntityFrameworkCore;

namespace DataLayer
{
    public static class BookQueries
    {
        public static Book GetBook_Flat_NoTracking(this LibationContext context, string productId)
            => context
                .Books
                .AsNoTracking()
                .GetBook(productId);

        public static Book GetBook(this IQueryable<Book> books, string productId)
            => books
                .GetBooks()
                .SingleOrDefault(b => b.AudibleProductId == productId);

        /// <summary>This is still IQueryable. YOU MUST CALL ToList() YOURSELF</summary>
        public static IQueryable<Book> GetBooks(this IQueryable<Book> books, Expression<Func<Book, bool>> predicate)
            => books
                .GetBooks()
                .Where(predicate);

        /// <summary>This is still IQueryable. YOU MUST CALL ToList() YOURSELF</summary>
        public static IQueryable<Book> GetBooks(this IQueryable<Book> books)
            => books
                // owned items are always loaded. eg: book.UserDefinedItem, book.Supplements
                .Include(b => b.SeriesLink).ThenInclude(sb => sb.Series)
                .Include(b => b.ContributorsLink).ThenInclude(c => c.Contributor)
                .Include(b => b.Category).ThenInclude(c => c.ParentCategory);
    }
}