Owned Entity Types in EF Core

What are Owned Entities?

Owned entities are types that don’t have their own identity and are always accessed through their owner. They’re useful for value objects and complex types.

Basic Configuration

public class Order
{
    public int Id { get; set; }
    public Address ShippingAddress { get; set; }
    public Address BillingAddress { get; set; }
}

public class Address
{
    public string Street { get; set; }
    public string City { get; set; }
    public string ZipCode { get; set; }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Order>().OwnsOne(o => o.ShippingAddress);
    modelBuilder.Entity<Order>().OwnsOne(o => o.BillingAddress);
}

Table Splitting

// Owned entity stored in same table
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Order>().OwnsOne(o => o.ShippingAddress, sa =>
    {
        sa.Property(a => a.Street).HasColumnName("ShippingStreet");
        sa.Property(a => a.City).HasColumnName("ShippingCity");
        sa.Property(a => a.ZipCode).HasColumnName("ShippingZipCode");
    });
}

Separate Table

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Order>().OwnsOne(o => o.ShippingAddress, sa =>
    {
        sa.ToTable("ShippingAddresses");
    });
}

Collections of Owned Types

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Address> Addresses { get; set; }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Customer>().OwnsMany(c => c.Addresses, a =>
    {
        a.WithOwner().HasForeignKey("CustomerId");
        a.Property<int>("Id");
        a.HasKey("Id");
    });
}

Summary

Owned entities in EF Core represent value objects without identity. Configure using OwnsOne/OwnsMany. They can be stored in the same table or separate tables.