Allow Shared Columns with ComplexType

[FuJa0815]

Bug description

Currently, in a TPH mapped table properties of a ComplexType with the same column name do not share columns.

The code in "Your code" creates this migration:

migrationBuilder.CreateTable(
    name: "Thing",
    columns: table => new
    {
        Id = table.Column<int>(type: "INTEGER", nullable: false)
            .Annotation("Sqlite:Autoincrement", true),
        Discriminator = table.Column<string>(type: "TEXT", maxLength: 5, nullable: false),
        Address_City = table.Column<string>(type: "TEXT", nullable: true),
        Address_Street = table.Column<string>(type: "TEXT", nullable: true),
        Address_City1 = table.Column<string>(type: "TEXT", nullable: true),
        Address_Street1 = table.Column<string>(type: "TEXT", nullable: true)
    },
    constraints: table =>
    {
        table.PrimaryKey("PK_Thing", x => x.Id);
    });

It should map the 4 Address columns to 2.
Workarounds:

• Use THC or THT mapping
• Use something like this:

public abstract class Thing
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; init; }

    [Column(nameof(Address))]
    protected Address? Address { get; set; }
}

public sealed class ThingA : Thing
{
    [NotMapped]
    public new required Address Address { get => base.Address!; set => base.Address = value; }
}
public sealed class ThingB : Thing
{
    [NotMapped]
    public new required Address Address { get => base.Address!; set => base.Address = value; }
}

Your code

public class TestContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder options)
    {
        options.UseSqlite($"DataSource=:memory:");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Thing>()
            .HasDiscriminator()
            .HasValue<ThingA>("A")
            .HasValue<ThingB>("B");
    }
}

[ComplexType]
public record class Address(string Street, string City);

public abstract class Thing
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; init; }
}

public sealed class ThingA : Thing
{
    [Column(nameof(Address))]
    public required Address Address { get; set; }
}
public sealed class ThingB : Thing
{
    [Column(nameof(Address))]
    public required Address Address { get; set; }
}

Stack traces

Verbose output

EF Core version

10.0.9

Database provider

No response

Target framework

.NET 10

Operating system

No response

IDE

No response

[AndriySvyryd]

Instead of moving Address to the base type, you can keep the natural per-subtype required Address properties and simply force the inner property column names to identical values on both subtypes.
EF then collapses them into one shared set of columns.
 

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Thing>()
        .HasDiscriminator().HasValue<ThingA>("A").HasValue<ThingB>("B");

    modelBuilder.Entity<ThingA>().ComplexProperty(e => e.Address, a =>
    {
        a.Property(p => p.Street).HasColumnName("Address_Street");
        a.Property(p => p.City).HasColumnName("Address_City");
    });
    modelBuilder.Entity<ThingB>().ComplexProperty(e => e.Address, a =>
    {
        a.Property(p => p.Street).HasColumnName("Address_Street");
        a.Property(p => p.City).HasColumnName("Address_City");
    });
}