[Bug]: The Property uses ValueGenerator in complex FK is not tracked correctly

[mseada94]

Setup

• Two entities having one-to-many relation with a composite foreign key. (One Author Has Many Books)
• The relation is optional and not required.
• One of the key properties is generated using custom ValueGenerator<Guid>. (TenantId)

Error and notes

When adding a book with no author without setting the TenantId

• The value has been generated and could be shown as the CurrentValue for TenantId prop when debugging the EntityEntry
• The following error is returned:

The value of 'Book.TenantId' is unknown when attempting to save changes. This is because the property is also part of a foreign key for which the principal entity in the relationship is not known.

However, When adding a book with no author and **setting the TenantId Manually, Succeded with no errors.

I noticed a difference when debugging EntityEntry.InternalEntry.IsKeyUnknown is set with true in the first case and false in the second case.

Code Sample (Console App)
https://github.com/mohamed-seada-1994/EFCore-ValueGenerator-Bug-Sample

EF Core version:
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: NET 5.0
Operating system: Win10
IDE: Visual Studio 2019 16.9.6

[ajcvickers]

@mohamed-seada-1994 By default, EF Core assumes value generators generate values that can change from run to run. Starting in EF Core 6.0, this can be overridden on the value generator with GeneratesStableValues. For example:

    public class TenantIdGenerator : ValueGenerator<Guid>
    {
        public override Guid Next(EntityEntry entry)
            => Guid.Parse("98D06A82-C691-4988-EA39-08D98E2C8D8F");

        public override bool GeneratesTemporaryValues => false;

        public override bool GeneratesStableValues => true;
    }

I tested with your code using the EF Core 6.0 RC2 release and it results in both test cases passing.

[mseada94]

@ajcvickers Thank you for your answer.

For now, I need to find a solution for EF Core 5,
I am thinking of iterating over the added EntityEntry and resetting the property value on saveChanges

addedEntityEntry.Property("TenantId").CurrentValue = addedEntityEntry.Property("TenantId").CurrentValue;

I test this solution and it works.
Could this workaround cause any issues? and Is there a better workaround?

[ajcvickers]

@mohamed-seada-1994 That seems reasonable.

[mseada94]

@ajcvickers Thanks