Replacing Owned Entity that contains an enum value with .HasConversion<string> throws exception during SaveChanges

[bperc2]

After upgrading to preview versions of 7.0, I started encountering InvalidCastExceptions when saving changes to some of my entities. The specific scenario appears to be:

1. Replace an instance of an owned entity with a new instance
2. The owned entity contains an enum property that has been converted into a string
3. The value of that enum property has changed since it was loaded from the database

This all worked fine in EF Core 6.0 and 7.0.0-preview.3.22175.1. Preview 4 and beyond exhibit the issue.

Here is a runnable example to demonstrate.

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


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

// Setup
var project = new Project() { Title = "Test Project" };
project.Form.Quesion2 = MultipleChoiceOptions.A;
context.Projects.Add(project);

context.SaveChanges();

var project2 = context.Projects.First();
project2.Form.Quesion2 = MultipleChoiceOptions.B;
// This works fine
context.SaveChanges();

var project3 = context.Projects.First();
var replacementForm = new Form() { Question1 = "Updated", Quesion2 = MultipleChoiceOptions.B };
project3.Form = replacementForm;
// This also works fine because the value of the enum property didn't change
context.SaveChanges();

var project4 = context.Projects.First();
var replacementForm2 = new Form() { Quesion2 = MultipleChoiceOptions.C };
project4.Form = replacementForm2;
// This throws
context.SaveChanges();



public class AppDbContext : DbContext
{
    public DbSet<Project> Projects { get; set; }

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

    protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder)
    {
        configurationBuilder
            .Properties<Enum>()
            .HaveConversion<string>();
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.Entity<Project>(e =>
        {
            e.OwnsOne(p => p.Form, pf =>
            {

            });
        });
    }

}
    public class Project
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public Form Form { get; set; } = new();
    }

    public class Form
    {
        public string Question1 { get; set; } = "";
        public MultipleChoiceOptions? Quesion2 { get; set; }
    }

    public enum MultipleChoiceOptions
    {
        A,
        B,
        C,
        D
    }

Include stack traces

Exception message and stack trace

System.InvalidCastException
  HResult=0x80004002
  Message=Unable to cast object of type 'MultipleChoiceOptions' to type 'System.String'.
  Source=Microsoft.EntityFrameworkCore
  StackTrace:
   at Microsoft.EntityFrameworkCore.ChangeTracking.ValueComparer`1.Equals(Object left, Object right)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.ColumnValuePropagator.TryPropagate(IColumnMapping mapping, IUpdateEntry entry)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.GenerateColumnModifications()
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.get_ColumnModifications()
   at Microsoft.EntityFrameworkCore.Update.Internal.CommandBatchPreparer.<BatchCommands>d__8.MoveNext()
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.Execute(IEnumerable`1 commandBatches, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(IList`1 entriesToSave)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(StateManager stateManager, Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)

Provider and version information

EF Core version: 7.0.0-preview.4.22229.2 - 7.0.0-preview.7.22376.2
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 6.0
Operating system: Windows 10
IDE: Visual Studio 2022 17.3.0