Как мога да използвам Entity Framework върху обектна графика след дълбочина 2 с MySQL Connector / NET?

Редактиране

Тестът по-долу беше направен със SQL Server и SqlClient като доставчик. Фактът, че проблемът не може да се възпроизведе със SQL Server, повдига въпроса дали MySql доставчикът, който използвате, има грешка, която създава неправилен SQL за вашата LINQ заявка. Изглежда същия проблем като в този въпрос където проблемът е възникнал с MySql доставчик също и не може да бъде възпроизведен с SqlClient /SQL сървър.

Тествах примера с удебелен шрифт (с EF 4.3.1) и не мога да възпроизведа проблема:

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;

namespace EFInclude
{
    public class Harbor
    {
        public int HarborId { get; set; }
        public virtual ICollection<Ship> Ships { get; set; }

        public string Description { get; set; }
    }

    public class Ship
    {
        public int ShipId { get; set; }
        public int HarborId { get; set; }
        public virtual Harbor Harbor { get; set; }
        public virtual ICollection<CrewMember> CrewMembers { get; set; }

        public string Description { get; set; }
    }

    public class CrewMember
    {
        public int CrewMemberId { get; set; }
        public int ShipId { get; set; }
        public virtual Ship Ship { get; set; }
        public int RankId { get; set; }
        public virtual Rank Rank { get; set; }
        public int ClearanceId { get; set; }
        public virtual Clearance Clearance { get; set; }

        public string Description { get; set; }
    }

    public class Rank
    {
        public int RankId { get; set; }
        public virtual ICollection<CrewMember> CrewMembers { get; set; }

        public string Description { get; set; }
    }

    public class Clearance
    {
        public int ClearanceId { get; set; }
        public virtual ICollection<CrewMember> CrewMembers { get; set; }

        public string Description { get; set; }
    }

    public class MyContext : DbContext
    {
        public DbSet<Harbor> Harbors { get; set; }
        public DbSet<Ship> Ships { get; set; }
        public DbSet<CrewMember> CrewMembers { get; set; }
        public DbSet<Rank> Ranks { get; set; }
        public DbSet<Clearance> Clearances { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Database.SetInitializer(new DropCreateDatabaseAlways<MyContext>());

            using (var context = new MyContext())
            {
                context.Database.Initialize(true);

                var harbor = new Harbor
                {
                    Ships = new HashSet<Ship>
                    {
                        new Ship
                        {
                            CrewMembers = new HashSet<CrewMember>
                            {
                                new CrewMember
                                {
                                    Rank = new Rank { Description = "Rank A" },
                                    Clearance = new Clearance { Description = "Clearance A" },
                                    Description = "CrewMember A"
                                },
                                new CrewMember
                                {
                                    Rank = new Rank { Description = "Rank B" },
                                    Clearance = new Clearance { Description = "Clearance B" },
                                    Description = "CrewMember B"
                                }
                            },
                            Description = "Ship AB"
                        },
                        new Ship
                        {
                            CrewMembers = new HashSet<CrewMember>
                            {
                                new CrewMember
                                {
                                    Rank = new Rank { Description = "Rank C" },
                                    Clearance = new Clearance { Description = "Clearance C" },
                                    Description = "CrewMember C"
                                },
                                new CrewMember
                                {
                                    Rank = new Rank { Description = "Rank D" },
                                    Clearance = new Clearance { Description = "Clearance D" },
                                    Description = "CrewMember D"
                                }
                            },
                            Description = "Ship CD"
                        }
                    },
                    Description = "Harbor ABCD"
                };

                context.Harbors.Add(harbor);
                context.SaveChanges();
            }

            using (var context = new MyContext())
            {
                DbSet<Harbor> dbSet = context.Set<Harbor>();
                IQueryable<Harbor> query = dbSet;
                query = query.Include(entity => entity.Ships);
                query = query.Include(entity => entity.Ships.Select(s => s.CrewMembers));
                query = query.Include(entity => entity.Ships.Select(s => s.CrewMembers.Select(cm => cm.Rank)));
                query = query.Include(entity => entity.Ships.Select(s => s.CrewMembers.Select(cm => cm.Clearance)));

                var sqlString = query.ToString();
                // see below for the generated SQL query

                var harbor = query.Single();

                Console.WriteLine("Harbor {0} Description = \"{1}\"",
                    harbor.HarborId, harbor.Description);
                foreach (var ship in harbor.Ships)
                {
                    Console.WriteLine("- Ship {0} Description = \"{1}\"",
                        ship.ShipId, ship.Description);
                    foreach (var crewMember in ship.CrewMembers)
                    {
                        Console.WriteLine("-- CrewMember {0} Description = \"{1}\"", 
                            crewMember.CrewMemberId, crewMember.Description);
                        Console.WriteLine("-- CrewMember {0} Rank Description = \"{1}\"",
                            crewMember.CrewMemberId, crewMember.Rank.Description);
                        Console.WriteLine("-- CrewMember {0} Clearance Description = \"{1}\"",
                            crewMember.CrewMemberId, crewMember.Clearance.Description);
                    }
                }

                Console.ReadLine();
            }
        }
    }
}

Резултатът е:

Според описанието ви с удебелен шрифт трябва да имам:CrewMember 1 Description ="Rank A" и същата бъркотия за останалите 3 членове на екипажа. Но аз нямам това.

Има ли нещо различно в моята тестова програма в сравнение с вашия код, където имате грешката?

Редактиране

Генерираният SQL за заявката (вижте реда var sqlString = query.ToString(); в изходния код по-горе, следното е съдържанието на sqlString ) е:

SELECT 
[Project1].[HarborId] AS [HarborId], 
[Project1].[Description] AS [Description], 
[Project1].[C2] AS [C1], 
[Project1].[ShipId] AS [ShipId], 
[Project1].[HarborId1] AS [HarborId1], 
[Project1].[Description1] AS [Description1], 
[Project1].[C1] AS [C2], 
[Project1].[CrewMemberId] AS [CrewMemberId], 
[Project1].[ShipId1] AS [ShipId1], 
[Project1].[RankId] AS [RankId], 
[Project1].[ClearanceId] AS [ClearanceId], 
[Project1].[Description2] AS [Description2], 
[Project1].[RankId1] AS [RankId1], 
[Project1].[Description3] AS [Description3], 
[Project1].[ClearanceId1] AS [ClearanceId1], 
[Project1].[Description4] AS [Description4]
FROM ( SELECT 
    [Extent1].[HarborId] AS [HarborId], 
    [Extent1].[Description] AS [Description], 
    [Join3].[ShipId1] AS [ShipId], 
    [Join3].[HarborId] AS [HarborId1], 
    [Join3].[Description1] AS [Description1], 
    [Join3].[CrewMemberId] AS [CrewMemberId], 
    [Join3].[ShipId2] AS [ShipId1], 
    [Join3].[RankId1] AS [RankId], 
    [Join3].[ClearanceId1] AS [ClearanceId], 
    [Join3].[Description2] AS [Description2], 
    [Join3].[RankId2] AS [RankId1], 
    [Join3].[Description3] AS [Description3], 
    [Join3].[ClearanceId2] AS [ClearanceId1], 
    [Join3].[Description4] AS [Description4], 
    CASE WHEN ([Join3].[ShipId1] IS NULL) THEN CAST(NULL AS int) WHEN ([Join3].[CrewMemberId] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1], 
    CASE WHEN ([Join3].[ShipId1] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C2]
    FROM  [dbo].[Harbors] AS [Extent1]
    LEFT OUTER JOIN  (SELECT [Extent2].[ShipId] AS [ShipId1], [Extent2].[HarborId] AS [HarborId], [Extent2].[Description] AS [Description1], [Join2].[CrewMemberId], [Join2].[ShipId2], [Join2].[RankId1], [Join2].[ClearanceId1], [Join2].[Description2], [Join2].[RankId2], [Join2].[Description3], [Join2].[ClearanceId2], [Join2].[Description4]
        FROM  [dbo].[Ships] AS [Extent2]
        LEFT OUTER JOIN  (SELECT [Extent3].[CrewMemberId] AS [CrewMemberId], [Extent3].[ShipId] AS [ShipId2], [Extent3].[RankId] AS [RankId1], [Extent3].[ClearanceId] AS [ClearanceId1], [Extent3].[Description] AS [Description2], [Extent4].[RankId] AS [RankId2], [Extent4].[Description] AS [Description3], [Extent5].[ClearanceId] AS [ClearanceId2], [Extent5].[Description] AS [Description4]
            FROM   [dbo].[CrewMembers] AS [Extent3]
            INNER JOIN [dbo].[Ranks] AS [Extent4] ON [Extent3].[RankId] = [Extent4].[RankId]
            LEFT OUTER JOIN [dbo].[Clearances] AS [Extent5] ON [Extent3].[ClearanceId] = [Extent5].[ClearanceId] ) AS [Join2] ON [Extent2].[ShipId] = [Join2].[ShipId2] ) AS [Join3] ON [Extent1].[HarborId] = [Join3].[HarborId]
)  AS [Project1]
ORDER BY [Project1].[HarborId] ASC, [Project1].[C2] ASC, [Project1].[ShipId] ASC, [Project1].[C1] ASC