[release/10.0] Fix owned entities with default values not saved in TPH with shared columns

[Copilot]

Fixes #37525

Description
When using Table-Per-Hierarchy (TPH) inheritance with owned entities (OwnsOne) where different entity types share column names via .HasColumnName(), setting an owned entity from null to a new instance with all CLR default values (e.g., EnumValue.Unknown = 0, IsBool = false) silently dropped the UPDATE columns — the owned entity remained null in the database.

ColumnValuePropagator.TryPropagate treats sentinel values on Added entries as "nothing to write." This is correct when another entry recorded a different value for the shared column, but wrong when the Added entry is the sole writer — the sentinel is the intended value.

Customer impact
Customers using TPH with owned entities sharing column names cannot save owned entities with default values. The data silently remains null in the database, leading to data corruption. No workaround other than avoiding default values or not sharing column names.

How found
Customer reported.

Regression
Yes, from EF Core 7.

Testing
Test added.

Risk
Low. The fix only affects saving changes in TPH with shared columns. Quirk mode added

Original prompt

---

This section details on the original issue you should resolve

<issue_title>OwnOne entities with default values not saved in TPH scenario</issue_title>
<issue_description>### Bug description

When using Table-Per-Hierarchy (TPH) inheritance with owned entities (OwnsOne), EF Core 8 generates an UPDATE statement but omits the owned entity columns when:

• An owned entity property starts as null in the database
• It's then set to an instance where all properties have their CLR default values (e.g., EnumValue.Unknown = 0, IsBool = false)
• Nullable reference types are disabled (disable in the project file)

This leads to data corruption, preventing us from effectively upgrading from EF core 7 to EF core 8/9/10.

Please find a sample repro project attached.
EfCoreEnumNullTest.zip

EF Core version

8/9/10

Database provider

SqlServer

Target framework

.NET 10

IDE

rider</issue_description>

<agent_instructions>Start by creating a test that fails in the described way based on the comment #37525 (comment)</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@roji # AI answer

Reproduction Confirmed

I've successfully reproduced this issue. This is a regression affecting EF Core 8 and 9, which has been fixed in EF Core 10.

Symptoms

When using TPH (Table-Per-Hierarchy) inheritance with owned entities (OwnsOne) where <Nullable>disable</Nullable> is set in the project, and setting an owned entity with CLR default values (e.g., EnumValue.Unknown = 0, IsBool = false), EF Core 8/9 fails to generate an UPDATE statement. This results in the database retaining NULL values instead of the expected default values.

Version Testing Results

EF Core 7: ✅ Works correctly - generates UPDATE statement with owned entity columns
EF Core 8: ❌ Broken - no UPDATE statement generated, values remain NULL
EF Core 9: ❌ Broken - no UPDATE statement generated, values remain NULL
EF Core 10: ✅ Fixed - generates UPDATE statement with owned entity columns

Minimal repro

await using var context = new BlogContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

var childA = new ChildA();
context.Parents.Add(childA);
await context.SaveChangesAsync();
var childId = childA.Id;

context.ChangeTracker.Clear();

var loaded = await context.Parents.OfType<ChildA>().SingleAsync(c => c.Id == childId);
loaded.SetShared(SharedType.Create(EnumValue.Unknown, false));

await context.SaveChangesAsync();

context.ChangeTracker.Clear();

var verified = await context.Parents.OfType<ChildA>().SingleAsync(c => c.Id == childId);
Console.WriteLine($"EnumValue: {verified.Shared?.EnumValue} (expected: Unknown)");
Console.WriteLine($"IsBool: {verified.Shared?.IsBool} (expected: False)");

public abstract class Parent
{
    public int Id { get; set; }
}

public class ChildA : Parent
{
    public SharedType Shared { get; private set; }

    public void SetShared(SharedType shared)
    {
        Shared = shared ?? throw new ArgumentNullException(nameof(shared));
    }
}

public class ChildB : Parent
{
    public SharedType Shared { get; private set; }

    public void SetShared(SharedType shared)
    {
        Shared = shared ?? throw new ArgumentNullException(nameof(shared));
    }
}

public class SharedType
{
    protected SharedType() { }

    private SharedType(EnumValue enumValue, bool isBool)
    {
        EnumValue = enumValue;
        IsBool = isBool;
    }

    public EnumValue EnumValue { get; private set; }
    public bool IsBool { get; private set; }

    public static SharedType Create(EnumValue enumValue, bool isBool)
        => new(enumValue, isBool);
}

public enum EnumValue
{
    Unknown,
    Pass,
    Fail
}

public class BlogContext : DbContext
{
    public DbSet<Parent> Parents => Set<Parent>();

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer(Environment.GetEnvironmentVariable("Test__SqlServer__DefaultConnection"))
            .LogTo(Console.WriteLine, Microsoft.Extensions.Logging.LogLevel.Information)
            .EnableSensitiveDataLogging();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Parent>()
            .HasDiscriminator<string>("ChildType")
            .HasValue<ChildA>("ChildA")
            .HasValue<ChildB>("ChildB");

        modelBuilder.Entity<ChildA>().OwnsOne(c => c.Shared, sb =>
        {
            sb.Property(s => s.EnumValue).HasConversion<string>();
        });

        modelBuilder.Entity<ChildB>().OwnsOne(c => c.Shared, sb =>
        {
            sb.Property(s => s.EnumValue).HasConversion<string>();
        });
    }
}

</...

• Fixes OwnOne entities with default values not saved in TPH scenario #37525

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Pull request overview

This PR fixes a regression in EF Core 8/9/10 where owned entities with default values were not saved when using Table-Per-Hierarchy (TPH) inheritance with shared column names. The issue occurred because the ColumnValuePropagator.TryPropagate method incorrectly suppressed writes for sentinel values even when the Added entry was the sole writer for a shared column.

Changes:

• Added a guard condition to TryPropagate that only suppresses sentinel value writes when another entry has recorded a different value for the shared column
• Added comprehensive test coverage with a TPH model using owned entities, shared column names, and value converters
• Added test model classes (Nougat, CrunchyNougat, SoftNougat, NougatFilling, NougatFillingKind) to the Updates test infrastructure

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/EFCore.Relational/Update/ModificationCommand.cs	Fixed ColumnValuePropagator.TryPropagate to add an additional guard that compares _currentValue with the entry's provider value before suppressing sentinel writes
test/EFCore.Specification.Tests/Update/UpdatesTestBase.cs	Added model configuration for Nougat entities with owned Filling and string value converter on enum property
test/EFCore.Specification.Tests/TestModels/UpdatesModel/UpdatesContext.cs	Added DbSet properties for CrunchyNougat and SoftNougat
test/EFCore.Specification.Tests/TestModels/UpdatesModel/Nougat.cs	Added TPH test model with owned entities containing default values (enum = 0, bool = false)
test/EFCore.Relational.Specification.Tests/Update/UpdatesRelationalTestBase.cs	Added test method and model configuration with shared column names (FillingKind, FillingIsFresh) for the TPH scenario