ThenInclude chain on One-To-Many Reflection doesn't map objects from sql query

[nehio]

Introduction

I have not seen anything in other bugs related to this behaviour in current open issues. I will describe as best i can the behaviour. Here is the link of a small repo reproducing the issue : Test repo

Models

        public class ApplicationUser
        {
            [Key]
            public int Id { get; set; }

            public string LastName { get; set; }


            public string FirstName { get; set; }

            public UserInformation Information { get; set; }
        }

        public class UserInformation
        {
            [Key]
            public int Id { get; set; }
            public List<UserInformationPhoneNumber> PhoneNumbers { get; set; }

            public ApplicationUser User { get; set; }
        }

        public class UserInformationPhoneNumber
        {

            public UserInformationPhoneNumber()
            {
                PhoneNumber = new PhoneNumber();
            }

            public UserInformationPhoneNumber(PhoneNumber p)
            {
                PhoneNumber = p;
            }

            public UserInformation UserInformation { get; set; }

            [ForeignKey("UserInformation")]
            public int UserInformationId { get; set; }

            public PhoneNumber PhoneNumber { get; set; }

            [ForeignKey("PhoneNumber")]
            public int PhoneNumberId { get; set; }
        }

        public class PhoneNumber
        {

            [Key]
            public int Id { get; set; }

            public string Value { get; set; }

        }

Relations definition

        protected override void OnModelCreating(ModelBuilder builder)
        {
            builder.Entity<ApplicationUser>(entity =>
            {
                entity.HasOne(p => p.Information)
                .WithOne(i => i.User)
                .HasForeignKey<UserInformation>(b => b.Id);
            });

            builder.Entity<UserInformationPhoneNumber>()
            .HasKey(u => new { u.PhoneNumberId, u.UserInformationId });

            // These are not really required as the relations are defined in the classes themselves
            // The behaviour does not change by adding these
            //builder.Entity<UserInformationPhoneNumber>().HasOne(s => s.UserInformation).WithMany(s => s.PhoneNumbers).HasForeignKey(s => s.UserInformationId);
            //builder.Entity<UserInformationPhoneNumber>().HasOne(s => s.PhoneNumber).WithMany().HasForeignKey(s => s.PhoneNumberId);
        }

Adding mock data to query against

 private void AddUserToAppplication()
        {

            _context.ApplicationUsers.Add(new ApplicationUser
            {
                FirstName = "Name",
                LastName = "LastName",
                Information = new UserInformation
                {
                    PhoneNumbers = new List<UserInformationPhoneNumber>()
                    {
                        new UserInformationPhoneNumber
                        {
                            PhoneNumber = new PhoneNumber
                            {
                                Value = "+33 06 12 34 56 78"
                            }
                        }
                    }
                }
            });

            _context.SaveChanges();
        }

Bug part

 public IActionResult Index()
        {

            if (!_context.ApplicationUsers.Any())
            {
                AddUserToAppplication();
            }
            var query = _context.ApplicationUsers
                .Include(s => s.Information)
                .ThenInclude(s => s.PhoneNumbers)
                .ThenInclude(s => s.PhoneNumber) // Include generates empty objects with no Id or Values set
                .FirstOrDefault(s=> s.FirstName=="Name");
            
            return View();
        }

Expected behaviour

query returns a single "ApplicationUser" wich has within Information a single entry in the PhoneNumbers, wich contains a single PhoneNumber item containing the phone number.

Actual behaviour

PhoneNumber is an empty object with Id 0 and Value null (same is multiple PhoneNumber items), while the previous navigation property knows there's a ForeignKey for PhoneNumber with Id 1 that exists in the DB, the values are just not mapped when chained to the next .ThenInclude() .

** Sql generated **

SELECT [t].[Id], [t].[FirstName], [t].[LastName], [t].[Id0], [t0].[PhoneNumberId], [t0].[UserInformationId], [t0].[Id], [t0].[Value]
FROM (
    SELECT TOP(1) [a].[Id], [a].[FirstName], [a].[LastName], [u].[Id] AS [Id0]
    FROM [ApplicationUsers] AS [a]
    LEFT JOIN [UserInformation] AS [u] ON [a].[Id] = [u].[Id]
    WHERE [a].[FirstName] = N'Name'
) AS [t]
LEFT JOIN (
    SELECT [u0].[PhoneNumberId], [u0].[UserInformationId], [p].[Id], [p].[Value]
    FROM [UserInformationPhoneNumber] AS [u0]
    INNER JOIN [PhoneNumber] AS [p] ON [u0].[PhoneNumberId] = [p].[Id]
) AS [t0] ON [t].[Id0] = [t0].[UserInformationId]
ORDER BY [t].[Id], [t].[Id0], [t0].[PhoneNumberId], [t0].[UserInformationId], [t0].[Id]

This query executed in SSMS returns :

Where we can see that the query itselfs returns the PhoneNumber.Value and PhoneNumber.Id

But while running we can see that PhoneNumber mapping was ignored once returned from SQL.

I hope that i haven't missed anything configuration wise, but this seemes like a pretty straightforward query that should work.

Provider and version information

EF Core version: 5.0.3
Visual Studio 16.8.6
Database provider: Microsoft.EntityFrameworkCore.SqlServer 2019
Target framework: NET 5.0 (core)
Operating system: Windows 10 20H2
IDE: (e.g. Visual Studio 2019 16.3)

[anranruye]

I think the issue is caused by:

            public UserInformationPhoneNumber()
            {
                PhoneNumber = new PhoneNumber(); //comment this line may help
            }

[nehio]

You are quite correct @anranruyye. Is this a design choice ? Should the mapping of the object returned from DB be ignored if there's a constructor for a new empty PhoneNumber ? This code worked on EF Core 2.1 and would map objects without a problem.

[smitpatel]

Refer to #18007

[nehio]

Thank you for your answers on this matter