Fix nullable complex property with PropertyValues.ToObject() creating instance instead of null

[Copilot]

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        Fixes #bugnumber

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Description

When calling OriginalValues.ToObject() or CurrentValues.ToObject() on an entity with a nullable complex property that is null, the returned object incorrectly contains an instantiated complex type with default values instead of null.

public sealed class Product
{
    public int Id { get; private set; }
    public required string Name { get; set; }
    public Price? Price { get; set; }  // null
}

var product = await context.Products.FirstAsync();
var originalProduct = context.Entry(product).OriginalValues.ToObject();
// Bug: originalProduct.Price is non-null with Amount=0, CurrencyId=0
// Expected: originalProduct.Price is null

Root cause: When cloning property values, value type properties inside nullable complex types (e.g., decimal Amount) store default values rather than null when the complex property is null. The materializer cannot distinguish between "complex property is null" and "complex property has default values."

Changes

• PropertyValues: Added NullableComplexProperties list to track nullable non-collection complex properties for the structural type.
• ArrayPropertyValues: Added _nullComplexPropertyFlags as a bool[] with indices matching NullableComplexProperties ordering. ToObject() now sets tracked properties to null after materialization. Clone() copies the flags array.
• EntryPropertyValues: Clone() now uses the entry indexer to check nullable non-collection complex properties and sets the flags in the cloned instance when null.
• Added OptionalMilk property to existing Building class for testing nullable complex properties.
• Added test Nullable_complex_property_with_null_value_returns_null_when_using_ToObject()

Original prompt

---

This section details on the original issue you should resolve

<issue_title>EF 10: Nullable complex property with PropertyValues.ToObject() creates instance instead of null</issue_title>
<issue_description>### Bug description

When using a nullable complex type configured with ComplexProperty, calling OriginalValues.ToObject() when the original complex property value is null creates a complex type instance instead of returning null (same for CurrentValues.ToObject()).

Your code

#:package Npgsql.EntityFrameworkCore.PostgreSQL@10.0.0
#:property PublishAot=false

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

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

context.Products.Add(new() { Name = "Product 1" });
await context.SaveChangesAsync();

context.ChangeTracker.Clear();
var product = await context.Products.FirstAsync();
var originalProduct = context.ChangeTracker.Entries().First().OriginalValues.ToObject();
;

public sealed class ProductContext : DbContext
{
    public DbSet<Product> Products { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseNpgsql("Host=localhost;Username=postgres;Password=postgres;Database=Test")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
        => modelBuilder.Entity<Product>().ComplexProperty(x => x.Price);
}

public sealed class Product
{
    public int Id { get; private set; }
    public required string Name { get; set; }
    public Price? Price { get; set; }
}

public sealed class Price
{
    public required decimal Amount { get; init; }
    public required int CurrencyId { get; init; }
}

Stack traces

Verbose output

EF Core version

10.0.0

Database provider

Npgsql.EntityFrameworkCore.PostgreSQL

Target framework

.NET 10.0

Operating system

Windows 11

IDE

VSCode</issue_description>

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

@roji @AndriySvyryd here's a minimal SQL Server repro (very close to the above), in case it helps:

Minimal repro with SQL Server

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

context.Products.Add(new() { Name = "Product 1" });
await context.SaveChangesAsync();

context.ChangeTracker.Clear();
var product = await context.Products.FirstAsync();
var originalProduct = (Product)context.ChangeTracker.Entries().First().OriginalValues.ToObject();
Console.WriteLine("Original Product: " + originalProduct.Price?.Amount); // 0, should be null

public sealed class ProductContext : DbContext
{
    public DbSet<Product> Products { get; set; }

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

    protected override void OnModelCreating(ModelBuilder modelBuilder)
        => modelBuilder.Entity<Product>().ComplexProperty(x => x.Price);
}

public sealed class Product
{
    public int Id { get; private set; }
    public required string Name { get; set; }
    public Price? Price { get; set; }
}

public sealed class Price
{
    public required decimal Amount { get; init; }
    public required int CurrencyId { get; init; }
}

• Fixes EF 10: Nullable complex property with PropertyValues.ToObject() creates instance instead of null #37249

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[AndriySvyryd]

@copilot Make this bool[], with values in the same order as nullable non-collection complex properties for the given type base

[Copilot]

Changed to bool[] with values matching NullableComplexProperties ordering. Added NullableComplexProperties list to PropertyValues base class. Commit d13bfc9.

[AndriySvyryd]

@copilot GetValueInternal cannot be used for non-collection complex properties

[Copilot]

Fixed to use InternalEntry[nullableComplexProperties[i]] indexer instead of GetValueInternal. Commit d13bfc9.

[AndriySvyryd]

@copilot No need to do these actions, just use the newly added product. Also remove comments in this test

[Copilot]

Simplified test to use the newly added entity directly without SaveChanges/reload, and removed all comments. Commit d13bfc9.

[AndriySvyryd]

@copilot Remove, use an existing class instead

[Copilot]

Removed ProductWithNullableComplexType and ProductPrice. Added OptionalMilk property to the existing Building class instead. Commit d13bfc9.