The property '' on entity type '' has a temporary value while attempting to change the entity's state to 'Modified'

[cxc256]

I have a one to many relationship. I believe I have it set up correctly, please see the code below. A Batch will contain a bunch of Accounts. Everything works correctly when all objects are new and inserted into the database at once. However, there is a user case where Accounts are saved first, before being associated with a Batch. Then later, a Batch is created the existing batchless accounts are added to the Batch. When I try to save, I get the following error: The property 'BatchId' on entity type 'Account' has a temporary value while attempting to change the entity's state to 'Modified'. Either set a permanent value explicitly or ensure that the database is configured to generate values for this property.

I am using ASP.Net Core 3.1 with EF Core 3.1.6 for SQLServer. I'm using Visual Studio 2019 16.6 on Windows 10/2016

public class Batch
{
    private List<Account> _accounts;
    
    public int BatchId { get; set; }
    public int AccountCount { get; internal set; }
    public decimal AccountTotal { get; internal set; }
    public virtual IReadOnlyCollection<Account> Accounts => _accounts?.AsReadOnly( );
    
    public void AddAccount(Account account)
    {
        if( account == null )
            return;

        if( _accounts == null )
            _accounts = new List<Account>( );

        _accounts.Add( account );
        AccountCount++;
        AccountTotal += account.OriginalBalance;
    }
}

public class Account
{
    public int AccountId { get; set; }
    public decimal OriginalBalance { get; set; }
}

public class BatchConfig : IEntityTypeConfiguration<Batch>
{
    public void Configure( EntityTypeBuilder<Batch> builder )
    {
        if( builder == null )
            throw new ArgumentNullException( nameof( builder ) );

        builder.ToTable( "XXXXX" ).HasKey( e => e.BatchId );

        builder.Property( e => e.BatchId ).UseIdentityColumn( );

        builder
            .HasMany( e => e.Accounts )
            .WithOne( )
            .HasForeignKey( e => e.BatchId )
            .HasPrincipalKey( e => e.BatchId )
            ;

    }
}

public class AccountConfig : IEntityTypeConfiguration<Account>
{
    public void Configure( EntityTypeBuilder<Account> builder )
    {
        if( builder == null )
            throw new ArgumentNullException( nameof( builder ) );

        builder.ToTable( "XXXXX" ).HasKey( e => e.AccountId );
        builder.Property( e => e.AccountId ).UseIdentityColumn( );

        builder.Property( e => e.TotalAdjustments ).HasComputedColumnSql( "TotalAdjustments" );
        builder.Property( e => e.TotalDisbursements ).HasComputedColumnSql( "TotalDisbursements" );

        builder.Property( e => e.BatchId ).HasColumnName( "DepositBatchId" );

        builder
            .HasOne( e => e.CheckPayerCompany )
            .WithOne( )
            .HasForeignKey<Account>( e => e.CheckCompanyId );       

        builder
            .HasOne( e => e.AccountType )
            .WithOne( )
            .HasForeignKey<Account>( e => e.AccountTypeId );

        builder
            .HasOne( e => e.DepositTypeLookup )
            .WithOne( )
            .HasForeignKey<ClipAccount>( e => e.DepositType );

        builder
            .HasOne( e => e.EmployeeContribPercentage )
            .WithOne( )
            .HasForeignKey<Account>( e => e.EECPercentId );

        builder
            .HasOne( e => e.EmployerPensionContribPercentage )
            .WithOne( )
            .HasForeignKey<Account>( e => e.ERPPercentId );

        builder
            .HasOne( e => e.EmployerHealthContribPercentage )
            .WithOne( )
            .HasForeignKey<Account>( e => e.ERHPercentId );
    }
}

Steps to reproduce

1. Save an Account in the database.
2. In another session, pull that account from database.
3. Create new Batch
   4 .Call Batch.AddAccount(account)
4. Save Batch to Database

[ajcvickers]

@cxc256 The code snippets above do not compile and it's not clear what the missing parts should be. Please attach a small, runnable project or post a small, runnable code listing that reproduces what you are seeing so that we can investigate.

[cxc256]

@ajcvickers , attached is a sample. I used the internal custom repository pattern I'm required to use for the project.
EFCoreTest.zip

[ajcvickers]

@cxc256 Thanks for the repro code.

Note for team: the issue here is in changing from an Added state to a Modified state when the entity has a temporary FK value. See simplified repro code below. We currently throw, but for an FK it is valid to have a temporary value pointing to a new Added principal.

public class SomeDbContext : DbContext
{
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>();
    }
    
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer(Your.SqlServerConnectionString);
}

public static class Program
{
    public static void Main()
    {
        using (var context = new SomeDbContext())
        {
            context.Database.EnsureDeleted();
            context.Database.EnsureCreated();

            var post = new Post { Id = 1 };
            context.Add(post);
            
            var blog = new Blog();
            context.Add(blog);

            // Associate with the principal
            post.Blog = blog;

            // Works if this state change is done before associating the Added principal
            // Fails if it is done after, like here.
            context.Entry(post).State = EntityState.Modified;

            context.ChangeTracker.DetectChanges();
        }
    }
}

public class Blog
{
    public int Id { get; set; }
    public ICollection<Post> Posts { get; set; }
}

public class Post
{
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int Id { get; set; }
    
    public int? BlogId { get; set; }
    public Blog Blog { get; set; }
}

Unhandled exception. System.InvalidOperationException: The property 'BlogId' on entity type 'Post' has a temporary value while attempting to change the entity's state to 'Modified'. Either set a permanent value explicitly or ensure that the database is configured to generate values for this property.
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState oldState, EntityState newState, Boolean acceptChanges, Boolean modifyProperties)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState entityState, Boolean acceptChanges, Boolean modifyProperties, Nullable`1 forceStateWhenUnknownKey)
   at Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry.set_State(EntityState value)
   at Program.Main() in /home/ajcvickers/AllTogetherNow/Daily/Daily.cs:line 59

[AndriySvyryd]

Related: #14192