Efcore: List of owned IEquatable entity is cleared after SaveChangesAsync

Created on 12 Feb 2019 · 22Comments · Source: dotnet/efcore

In our project, we need the entity to map and do some handling after it is updated.
However, it seems that the list of IEquatable objects are cleared after SaveChangesAsync, and cause our handling to become incorrect.

We expect the updated entity will remain unchanged after SaveChangesAsync

Exception message: N/A
Stack trace: N/A

Steps to reproduce

```c#
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace TestEntityFrameworkCore
{
public class User
{
public Guid UserId { get; set; }
public string Email { get; set; }
public IReadOnlyList Roles => _roles.AsReadOnly();
private readonly List _roles = new List();

    public void SetRoles(IList<Role> roles)
    {
        if (_roles.Count == roles.Count &&
            !_roles.Except(roles).Any())
            return;

        _roles.Clear();
        _roles.AddRange(roles.Where(x => x != null).Distinct());
    }
}

public class Role : IEquatable<Role>
{
    public string Value { get; set; }
    public bool Equals(Role other)
        => Value == other.Value;
}

public class SqlDbContext : DbContext
{
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer(@"Server=.;Database=core;Trusted_Connection=True;");

    protected override void OnModelCreating(ModelBuilder builder) =>
        builder.Entity<User>(m =>
        {
            m.ToTable("User", "user");
            m.HasKey(x => x.UserId);
            m.OwnsMany(x => x.Roles, nav =>
            {
                nav.ToTable("UserRole", "user");
                nav.Property<Guid>("RoleAssignmentId");
                nav.HasKey("RoleAssignmentId");
                nav.Property(x => x.Value)
                    .HasColumnName("Role");
                nav.Property<Guid>("UserId");

                nav.HasForeignKey("UserId");
            }).UsePropertyAccessMode(PropertyAccessMode.Field);
        });
}

public class Program
{
    public static async Task Main()
    {
        using (var context = new SqlDbContext())
        {
            var user = await context.Set<User>()
                .Where(u => u.Email == "[email protected]")
                .FirstOrDefaultAsync(CancellationToken.None);

            // At this point user.Roles has 3 roles

            user.SetRoles(new List<Role> {
                new Role {
                    Value = "Basic"
                }
            });

            // At this point user.Roles has 1 "Basic" role
            await context.SaveChangesAsync(CancellationToken.None);

            var role = user.Roles; // At this point user.Roles has no item
            // But we expect user.Roles still have 1 "Basic" role for us to do some further handlings
        }
    }
}

}
```

Further technical details

EF Core version: 2.2.1
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows 10
IDE: Visual Studio 2017 15.9.6

closed-fixed customer-reported type-bug

Source

jasonycw

All 22 comments

@jasonycw What is your expectation around implementing IEquatable on the Role entity type? Do you expect EF to treat different instances that compare equal as the same?

ajcvickers on 21 Feb 2019

@ajcvickers In our case, Role is one of the ValueObject which is the one implemented IEquatable

``` C#
public class Role : ValueObject
{
public string Value { get; set; }
protected override IEnumerable

Efcore: List of owned IEquatable entity is cleared after SaveChangesAsync

Steps to reproduce

Further technical details

All 22 comments

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