Owned entities with one-to-many relationships in EF Core 3

Question

I'm trying to wrap my head around Owned Entities and relationships between them and other Entities. I'm working on a very simple example with Products, Quotes and QuoteItems:

public class Product
    {
        public Product(Guid id, decimal price, string name, DateTime creationDate)
        {
            Id = id;
            Price = price;
            Name = name;
            CreationDate = creationDate;
        }

        public Guid Id { get; }
        public decimal Price { get; }
        public string Name { get; }
        public DateTime CreationDate { get; }
    }

public class Quote
    {
        public Quote(Guid id, DateTime creationDate)
        {
            Id = id;
            CreationDate = creationDate;
            QuoteItems = new List<QuoteItem>();
        }

        public Guid Id { get; }
        public DateTime CreationDate { get; }
        public ICollection<QuoteItem> QuoteItems { get; }
    }


 public class QuoteItem
    {
        private QuoteItem() { }
        public QuoteItem(Guid id, Product product, int quantity)
        {
            Id = id;
            Quantity = quantity;
            Product = product;
        }

        public Guid Id { get; }
        public Product Product { get; }
        public int Quantity { get; }
    }

very easy, nothing fancy. Products and Quotes are to be considered the "aggregate root", while the QuoteItems of course are "value objects".

This is how I'm configuring the db context:

public class CommerceDbContext : DbContext
    {
        public CommerceDbContext(DbContextOptions<CommerceDbContext> options)
            : base(options)
        {
            Database.EnsureCreated();
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfiguration(new QuoteEntityTypeConfiguration()); 
        }

        public DbSet<Product> Products { get; set; }

        public DbSet<Quote> Quote { get; set; }
    }

internal class QuoteEntityTypeConfiguration : IEntityTypeConfiguration<Quote>
    {
        public void Configure(EntityTypeBuilder<Quote> builder)
        {
            builder.ToTable("Quotes", "dbo");

            builder.HasKey(r => r.Id);

            builder.Property(e => e.CreationDate);

            builder.OwnsMany(s => s.QuoteItems, b =>
            {
                b.ToTable("QuoteItems", "dbo");
                b.Property(e => e.Id);
                b.Property(e => e.Quantity);

                b.HasOne(e => e.Product)
                    .WithMany()
                    .HasForeignKey("ProductId");
            });
        }
    }

which generates exactly what I want:

notice how the QuoteItems table has a FK on Products. Actually it would be nice to have the QuoteId as just FK and not part of the PK, but I'll probably work on it later.

My problem now is that I can create Products with no problem, but when I try to create a quote and add that product I get this error:

Basically seems that adding a quote will add the product as well as a new entity on the db context, hence creating the issue. But the product has been created previously and correctly written into the db.

Any idea?

Answer 1

solved by loading the Product instance from the same DbContext used to save the Quote.