Does ProjectTo mostly work with Microsoft.EntityFrameworkCore.Cosmos?

[BlaiseD]

Is it possible to expand an owned Cosmos DB list using ProjectTo? e.g. modelBuilder.Entity<Thing>().OwnsMany(t => t.AlternateAddresses);

Configuration below:

    public class ThingModel
    {
        public string Id { get; set; } = Guid.NewGuid().ToString();
        public string Name { get; set; } = string.Empty;
        public string ProductName { get; set; } = "";
        public int SupplierID { get; set; }
        public int CategoryID { get; set; }
        public CategoryModel? Category { get; set; }

        public AddressModel? SupplierAddress { get; set; }

        public int[]? AlternateIDs { get; set; }

        public ICollection<AlternateAddressModel> AlternateAddresses { get; set; } = [];
    }

    public class CategoryModel
    {
        public int? CategoryID { get; set; }
        public string CategoryName { get; set; } = "";
    }

    public class AlternateAddressModel
    {
        public int AlternateAddressID { get; set; }
        public string City { get; set; } = "";
        public string? State { get; set; }
        public string? ZipCode { get; set; }
    }

    public class AddressModel
    {
        public int AddressID { get; set; }
        public string City { get; set; } = "";
        public string? State { get; set; }
        public string? ZipCode { get; set; }
    }

    public class Thing
    {
        public string Id { get; set; } = Guid.NewGuid().ToString();
        public string Name { get; set; } = string.Empty;
        public string ProductName { get; set; } = "";
        public int SupplierID { get; set; }
        public int CategoryID { get; set; }

        public Category? Category { get; set; }
        public Address? SupplierAddress { get; set; }

        public int[]? AlternateIDs { get; set; }
        public ICollection<AlternateAddress> AlternateAddresses { get; set; } = [];
    }

    public class Category
    {
        public int? CategoryID { get; set; }
        public string CategoryName { get; set; } = "";
    }

    public class AlternateAddress
    {
        public int AlternateAddressID { get; set; }
        public string City { get; set; } = "";
        public string? State { get; set; }
        public string? ZipCode { get; set; }

    }

    public class Address
    {
        public int AddressID { get; set; }
        public string City { get; set; } = "";
        public string? State { get; set; }
        public string? ZipCode { get; set; }

    }

    public class DataClassesMappings : Profile
    {
        public DataClassesMappings()
        {
            CreateMap<Address, AddressModel>()
                .ForAllMembers(o => o.ExplicitExpansion());
            CreateMap<AddressModel, Address>();
            CreateMap<AlternateAddress, AlternateAddressModel>()
                .ForMember(dest => dest.AlternateAddressID, opt => opt.MapFrom(src => src.AlternateAddressID))
                .ForMember(dest => dest.City, opt => opt.MapFrom(src => src.City))
                .ForMember(dest => dest.State, opt => opt.MapFrom(src => src.State))
                .ForMember(dest => dest.ZipCode, opt => opt.MapFrom(src => src.ZipCode))
                .ForAllMembers(o => o.ExplicitExpansion());
            CreateMap<AlternateAddressModel, AlternateAddress>();
            CreateMap<Category, CategoryModel>()
                .ForAllMembers(o => o.ExplicitExpansion());
            CreateMap<CategoryModel, Category>();
            CreateMap<Thing, ThingModel>()//ForMember expressions below needed for any expansion to work
                .ForMember(dest => dest.AlternateAddresses, opt => opt.MapFrom(src => src.AlternateAddresses == null ? new AlternateAddressModel[0] : src.AlternateAddresses.Select(a => new AlternateAddressModel
                {
                    AlternateAddressID = a.AlternateAddressID,
                    City = a.City,
                    State = a.State,
                    ZipCode = a.ZipCode
                }).ToArray()))
                .ForMember(dest => dest.Category, opt => opt.MapFrom(src => new CategoryModel
                {
                    CategoryID = src.Category.CategoryID,
                    CategoryName = src.Category.CategoryName
                }))
                .ForMember(dest => dest.SupplierAddress, opt => opt.MapFrom(src => new AddressModel
                {
                    AddressID = src.SupplierAddress.AddressID,
                    City = src.SupplierAddress.City
                }))
                .ForAllMembers(o => o.ExplicitExpansion());
            CreateMap<ThingModel, Thing>();
        }
    }

Please find a repro here. The results are the same using Testcontainers.CosmosDb or using an Azure resource. The OwnsOne expansions needed a workaround in the configuration. The OwnsMany attempt doesn't quite work. Oddly, the AlternateAddresses source collection seems to be null in ForMember handler. Known issues?

[BlaiseD]

The following does not work either -probably not an AutoMapper problem.

ThingModel[] things = (await dataClassesContext.Things.OrderBy(t => t.Id).AsNoTracking().Select
(
    t => new ThingModel
    {
        ProductName = t.ProductName,
        Id = t.Id,
        CategoryID = t.CategoryID,
        SupplierID = t.SupplierID,
        Category = new CategoryModel
        {
            CategoryID = t.Category.CategoryID,
            CategoryName = t.Category.CategoryName
        },
        SupplierAddress = new AddressModel
        {
            AddressID = t.SupplierAddress.AddressID,
            City = t.SupplierAddress.City
        },
        AlternateAddresses = t.AlternateAddresses == null ? new AlternateAddressModel[0] : t.AlternateAddresses.Select(a => new AlternateAddressModel
        {
            AlternateAddressID = a.AlternateAddressID,
            City = a.City,
            State = a.State,
            ZipCode = a.ZipCode
        }).ToList()
    }
).OrderBy(t => t.ProductName).ToListAsync(CancellationToken.None)).ToArray();
``

[jbogard]

We don't test our LINQ expressions on our providers (only EF Core). In general, you'll need to test the LINQ query by itself, without AutoMapper, to see if it works. That's how we built out the current support - verified LINQ queries, then generated them.