Encrypted attribute convention throws exception in Select projection in EF Core 9.0.0-rc.2.24474.1

[russcam]

Here's a minimal repro: https://github.com/russcam/efcore9-bug

Background

The EF Core configuration uses a convention to encrypt properties in the EF model that are attributed with an EncryptedAttribute.
This is done in an IModelFinalizingConvention by setting a value converter for those attributed properties

public class EncryptedConvention : IModelFinalizingConvention
{
    private readonly EncryptionConverter _encryptionConverter;

    public EncryptedConvention(IEncryptor encryptor) =>
        _encryptionConverter = new EncryptionConverter(encryptor);

    public void ProcessModelFinalizing(IConventionModelBuilder modelBuilder,
        IConventionContext<IConventionModelBuilder> context)
    {
        foreach (var entityType in modelBuilder.Metadata.GetEntityTypes())
        {
            foreach (var property in entityType.GetDeclaredProperties())
            {
                var encryptedAttribute = property.PropertyInfo?.GetCustomAttribute<EncryptedAttribute>();
                if (encryptedAttribute != null)
                    property.SetValueConverter(_encryptionConverter);
            }
        }
    }
}

Problem

When projecting an encrypted property in a .Select(...) projection such as

var users = await db.Users
        .AsNoTracking()
        .Select(u => new 
        {
            Username = u.Username,
            Encrypted = u.Encrypted,
        })
        .ToListAsync();

the following exception is thrown in EF Core 9.0.0-rc.2.24474.1

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at lambda_method43(Closure, QueryContext, DbDataReader, ResultContext, SingleQueryResultCoordinator)
   at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at Program.<Main>$(String[] args) in C:\Users\russc\source\EFCore9Bug\EFCore9Bug\Program.cs:line 22
   at Program.<Main>(String[] args)

Observations

• Removing the encrypted property from the select projection no longer throws the exception
• Calls that return the encrypted property without using projection do not throw an exception (example in the minimal repro is returning the alice entity).
• This works as expected with EF Core 8.0.10

Include provider and version information

EF Core version: 9.0.0-rc.2.24474.1
Database provider: Sqlite in the minimal repro, but also observe it with Postgres provider. It looks to be a core issue and not provider specific.
Target framework: net9.0
Operating system: Windows 11

[roji]

Duplicate of #34760

[roji]

@russcam thanks for the repro, I could indeed see the regression between 8.0 and 9.0. However, this has nothing to do with MemberMemberBinding - the cause is having a value converter which captures (closure). This has already been fixed for GA in #34760 - if you try the latest EF daily build, the problem goes away (I tried with 9.0.0-rtm.24514.19).

Regardless, thanks again for reporting (regardless of it ending up being a duplicate) - this is exactly the kind of report we need to make sure we're not regressing, etc.

For reference, here's the narrowed-down standalone repro I produced from your original repro above:

Narrowed-down repro

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

var users = await context.Users
    .Select(u => u.Encrypted)
    .ToListAsync();

public class AppDbContext : DbContext
{
    public DbSet<User> Users { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer("Server=localhost;Database=test;User=SA;Password=Abcd5678;Connect Timeout=60;ConnectRetryCount=0;Encrypt=false")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>(b =>
        {
            b.Property(u => u.Encrypted).HasConversion(x => Foo(x), x => Foo(x));
            b.HasData(new User { UserId = 1, Encrypted = "some value" });
        });
    }

    // Adding static to the below makes the error go away
    public string Foo(string value) => value;
}

public class User
{
    public int UserId { get; set; }
    public string Encrypted { get; set; } = default!;
}

[russcam]

Thanks for taking the time to review @roji!

[roji]

My pleasure!