Entity Framework Core OwnsOne Creates Separate Tables, Rather than adding properties to the Same Table as Expected

Question

I thought that Entity Framework Core owned types by default get added to the same table as their owner. But I'm not seeing this in the migration.

Would someone clue me in here?

Is there a way to get the desired migration with Name properties added directly to the Person table?

public class Person
{
    public Name Name { get; set; }
}

public class Name
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class PersonConfiguration : IEntityTypeConfiguration<Person>
{
    public void Configure(EntityTypeBuilder<Person> person)
    {
          person.OwnsOne(p => p.Name);
    }
}

dotnet ef migrations add DidNotSeeThatComing results in

public partial class DidNotSeeThatComing : Migration
{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.CreateTable(
            name: "Name",
            columns: table => new
            {
                FirstName = table.Column<string>(type: "varchar", nullable: true),
                LastName = table.Column<string>(type: "varchar", nullable: true),
                PersonId = table.Column<Guid>(nullable: false)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_Name", x => x.PersonId);
                table.ForeignKey(
                    name: "FK_Name_Person_PersonId",
                    column: x => x.PersonId,
                    principalTable: "Person",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Cascade);
            });
        );
    }
}

Answer 1

I created this myself unwittingly with this configuration code

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
   base.OnModelCreating(modelBuilder);
   foreach (var entity in modelBuilder.Model.GetEntityTypes())
   {
       entity.Relational().TableName = entity.Name;
   }
}

Here is the workaround I'm using

[Owned] // Microsoft.EntityFrameworkCore
public class Name { ... }

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
   base.OnModelCreating(modelBuilder);
   foreach (var entity in modelBuilder.Model.GetEntityTypes())
   {
       if(!entity.ClrType.GetCustomAttributes().OfType<OwnedAttribute>().Any())
       {
            entity.Relational().TableName = entity.Name;
       }
   }
}    

Answer 2

Try something like the following:

public class Person
{
    public Guid Id { get; set; }
    public Name Name { get; set; }
}

public class Name
{
    public Guid Id { get; set; }
    public Guid PersonId {get;set;}
    public Person Person { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class PersonConfiguration : IEntityTypeConfiguration<Person>
{
    public void Configure(EntityTypeBuilder<Person> person)
    {
        person.OwnsOne(p => p.Name,
            nCls =>
            {
                nCls.HasOne(n => n.Person);
                nCls.HasKey(n => new {n.Id, n.PersonId});
                nCls.HasForeignKey(m => m.PersonId);
                nCls.ToTable(nCls.OwnedEntityType.ClrType.Name);
            }
        );
    }
}

this should get you something like:

protected override void Up(MigrationBuilder migrationBuilder)
{
// the table names are lower case because my convention is to generate all names in snake_case

    migrationBuilder.CreateTable(
        name: "persons",
        columns: table => new
        {
            id = table.Column<Guid>(nullable: false)
        },
        constraints: table =>
        {
            table.PrimaryKey("pk_persons", x => x.id);
        });

    migrationBuilder.CreateTable(
        name: "name",
        columns: table => new
        {
            id = table.Column<Guid>(nullable: false),
            person_id = table.Column<Guid>(nullable: false),
            first_name = table.Column<string>(maxLength: 256, nullable: true),
            last_name = table.Column<string>(maxLength: 256, nullable: true)
        },
        constraints: table =>
        {
            table.PrimaryKey("pk_name", x => new { x.id, x.person_id });
            table.ForeignKey(
                name: "fk_name_persons_person_id",
                column: x => x.person_id,
                principalTable: "persons",
                principalColumn: "id",
                onDelete: ReferentialAction.Cascade);
        });
}

Answer 3

@Davious i had exact the same problem today thanks for sharing your solution. Here is my solution where you don't need the OwnedAttribute because you can also use entity.IsOwned(). I always try to do all confiugration via the DbContext.

///[Owned] // Not needed anymore
public class Name { ... }

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
   base.OnModelCreating(modelBuilder);
   modelbuilder.Entity<Person>().OwnsOne(p => p.Name)

   foreach (var entity in modelBuilder.Model.GetEntityTypes())
   {
       if(!entity.IsOwned())
       {
            entity.Relational().TableName = entity.Name;
       }
   }
}