using Microsoft.EntityFrameworkCore;

using System.Collections.Generic;

using System.Linq;

using System;

using AutoMapper;

using AutoMapper.Extensions.ExpressionMapping;  

using Microsoft.Extensions.Logging;

​

​

namespace EFTest

{

    public class Car

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public ICollection<Wheel> Wheels { get; set; }

    }

    public class Wheel

    {

        public int Id { get; set; }

        public int? FkCar { get; set; }

        public int FkBrand { get; set; }

        public string Name { get; set; }

        public virtual Car Car { get; set; }

        public virtual Brand Brand { get; set; }

    }

    public class Brand

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public ICollection<Wheel> Wheels { get; set; }

    }

    public class CarContext : DbContext

    {

        public CarContext(){ }

​

        public CarContext(DbContextOptions<CarContext> options)

            : base(options){ }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

        {

            base.OnConfiguring(optionsBuilder);

        }

​

        public DbSet<Car> Cars { get; set; }

        public DbSet<Wheel> Wheels { get; set; }

        public DbSet<Brand> CarBrands { get; set; } 

         protected override void OnModelCreating(ModelBuilder modelBuilder)

        {

            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity<Wheel>(entity =>

            {

                entity.HasOne(d => d.Car)

                    .WithMany(p => p.Wheels)

                    .HasForeignKey(d => d.Id);

                entity.HasOne(d => d.Brand)

                    .WithMany(p => p.Wheels)

                    .HasForeignKey(d => d.Id);

            });

        }

    }

​

    public class CarDto

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public List<int> BrandFks { get; set; }

    }

    public class CarService

    {

        private CarContext _context;

​

        public CarService(CarContext context)

        {

            _context = context;

        }

​

        public void FillDatabase()

        {

            var car1 = new Car {

                Name = "Car1",

                Wheels = new List<Wheel> {

                    {

                        new Wheel {

                            Name = "Wheel1",

                            Brand = new Brand {

                                Name = "Brand1"

                            }

                        }

                    }

                }

            };

            _context.Cars.Add(car1);

            var car2 = new Car {

                Name = "Car2",

                Wheels = new List<Wheel> {

                    {

                        new Wheel {

                            Name = "Wheel2",

                            Brand = new Brand {

                                Name = "Brand2"

                            }

                        }

                    }

                }

            };

            _context.Cars.Add(car2);

            _context.SaveChanges();

        }

    }

​

    class Program

    {

        static void Main(string[] args)

        {

            var optionsBuilder = new DbContextOptionsBuilder<CarContext>()

                .UseSqlServer(FiddleHelper.GetConnectionStringSqlServer())

                .UseLoggerFactory(LoggerFactory.Create(b => b

                    .AddConsole()

                    .AddFilter(level => level >= LogLevel.Information)))

                .EnableSensitiveDataLogging()

                .EnableDetailedErrors();

            Console.WriteLine("This is an example of using EF Core InMemory Database");

            Console.WriteLine("======================================================");

            Console.WriteLine("");

            var config = new MapperConfiguration(

                cfg => {

                    cfg.AddExpressionMapping();

​

                    cfg.CreateMap<Car, CarDto>()

                        .ForMember(dest => dest.BrandFks, opt => opt.MapFrom(source => source.Wheels.Select(x => x.FkBrand)));

                }

            );

            var mapper = config.CreateMapper();

​

            // Run the test against one instance of the context

            using (var context = new CarContext(optionsBuilder.Options))

            {

                context.Database.EnsureCreated();

                var service = new CarService(context);

                service.FillDatabase();

                var correct = context.Cars

                    .UseAsDataSource(mapper.ConfigurationProvider).For<CarDto>()

                    .Where(x => !x.BrandFks.Any())

                    .ToList();

                var suboptimal = context.Cars

                    .UseAsDataSource(mapper.ConfigurationProvider).For<CarDto>()

                    .AsEnumerable() // <-- switch to client evaluation

                    .Where(x => x.BrandFks == null)

                    .ToList();

            }

        }

    }

}