Program.cs

using Microsoft.EntityFrameworkCore;

var options = new DbContextOptionsBuilder<AppDbContext>()
	.UseSqlite("Data Source=:memory:")
	.Options;

using var db = new AppDbContext(options);
db.Database.OpenConnection();
db.Database.EnsureCreated();

var parentId = Guid.NewGuid();
db.Parents.Add(new Parent
{
	Id = parentId,
	Name = "P1",
	Coords = new Outer
	{
		First = new Inner { A = "1", B = "2" },
		Second = new Inner { A = "3", B = "4" }
	},
	Children = [new Child { Id = Guid.NewGuid(), ParentId = parentId, Data = new Inner { A = "x", B = "y" } }]
});
db.SaveChanges();

// Combining a collection-navigation struct projection with a nested-struct
// projection in the same Select works in preview.1 but throws in preview.2.
try
{
	var result = await db.Parents
		.AsNoTracking()
		.Where(p => p.Id == parentId)
		.Select(p => new ParentVm(
			p.Name,
			p.Children.Select(c => new ChildVm(new InnerVm(c.Data))).ToList(),
			new OuterVm(p.Coords)
		))
		.FirstOrDefaultAsync();

	Console.ForegroundColor = ConsoleColor.Green;
	Console.WriteLine($"OK — {result}");
	Console.ResetColor();
}
catch (InvalidOperationException ex)
{
	Console.ForegroundColor = ConsoleColor.Red;
	Console.WriteLine($"BUG: {ex.Message}");
	Console.ResetColor();
	Environment.ExitCode = 1;
}

// ── Domain ──────────────────────────────────────────────────────────

public readonly record struct Inner
{
	public string? A { get; init; }
	public string? B { get; init; }
}

public readonly record struct Outer
{
	public Inner First { get; init; }   // nested struct ComplexProperty
	public Inner Second { get; init; }  // nested struct ComplexProperty
}

public class Child
{
	public Guid Id { get; set; }
	public Guid ParentId { get; set; }
	public Inner Data { get; set; }     // struct ComplexProperty on collection element
	public Parent? Parent { get; set; }
}

public class Parent
{
	public Guid Id { get; set; }
	public string Name { get; set; } = default!;
	public Outer Coords { get; set; }   // struct with nested struct ComplexProperties
	public List<Child> Children { get; set; } = [];
}

// ── View models ─────────────────────────────────────────────────────

public record InnerVm(string? A, string? B)
{
	public InnerVm(Inner i) : this(i.A, i.B) { }
}

public record OuterVm(InnerVm First, InnerVm Second)
{
	public OuterVm(Outer o) : this(new InnerVm(o.First), new InnerVm(o.Second)) { }
}

public record ChildVm(InnerVm Data);
public record ParentVm(string Name, List<ChildVm> Children, OuterVm Coords);

// ── DbContext ───────────────────────────────────────────────────────

public class AppDbContext(DbContextOptions<AppDbContext> options) : DbContext(options)
{
	public DbSet<Parent> Parents => Set<Parent>();
	public DbSet<Child> Children => Set<Child>();

	protected override void OnModelCreating(ModelBuilder modelBuilder)
	{
		modelBuilder.Entity<Parent>(e =>
		{
			e.HasKey(x => x.Id);
			e.ComplexProperty(x => x.Coords, c =>
			{
				c.ComplexProperty(x => x.First, f =>
				{
					f.Property(x => x.A).HasColumnName("first_a");
					f.Property(x => x.B).HasColumnName("first_b");
				});
				c.ComplexProperty(x => x.Second, s =>
				{
					s.Property(x => x.A).HasColumnName("second_a");
					s.Property(x => x.B).HasColumnName("second_b");
				});
			});
			e.HasMany(x => x.Children).WithOne(x => x.Parent).HasForeignKey(x => x.ParentId);
		});

		modelBuilder.Entity<Child>(e =>
		{
			e.HasKey(x => x.Id);
			e.ComplexProperty(x => x.Data, d =>
			{
				d.Property(x => x.A).HasColumnName("data_a");
				d.Property(x => x.B).HasColumnName("data_b");
			});
		});
	}
}