Unblocking duplicate foreign keys when reverse engineering an existing database (SQL Server)

[ErikEJ]

I frequently see this error when users of SQL Server databases reverse engineer an existing database.

One possible solution could be to let the SQL Server scaffolding factory ignore the "second" foreign key. (and maybe just log a warning)

Thoughts?

System.InvalidOperationException: The foreign key {'Activity'} cannot be added to the entity type 'MyChild' because a foreign key on the same properties already exists on entity type 'MyChild' and also targets the key {'Oid'} on 'MyParent'.
   at void Microsoft.EntityFrameworkCore.Metadata.Internal.ForeignKey.Validate(IReadOnlyList<Property> properties, Key principalKey, EntityType declaringEntityType, EntityType principalEntityType)
   at new Microsoft.EntityFrameworkCore.Metadata.Internal.ForeignKey(IReadOnlyList<Property> dependentProperties, Key principalKey, EntityType dependentEntityType, EntityType principalEntityType, ConfigurationSource configurationSource)
   at ForeignKey Microsoft.EntityFrameworkCore.Metadata.Internal.EntityType.AddForeignKey(IReadOnlyList<Property> properties, Key principalKey, EntityType principalEntityType, ConfigurationSource? componentConfigurationSource, ConfigurationSource configurationSource)
   at IMutableForeignKey Microsoft.EntityFrameworkCore.Metadata.Internal.EntityType.Microsoft.EntityFrameworkCore.Metadata.IMutableEntityType.AddForeignKey(IReadOnlyList<IMutableProperty> properties, IMutableKey principalKey, IMutableEntityType principalEntityType)
   at IMutableForeignKey Microsoft.EntityFrameworkCore.Scaffolding.Internal.RelationalScaffoldingModelFactory.VisitForeignKey(ModelBuilder modelBuilder, DatabaseForeignKey foreignKey)
   at ModelBuilder Microsoft.EntityFrameworkCore.Scaffolding.Internal.RelationalScaffoldingModelFactory.VisitForeignKeys(ModelBuilder modelBuilder, IList<DatabaseForeignKey> foreignKeys)
   at ModelBuilder Microsoft.EntityFrameworkCore.Scaffolding.Internal.RelationalScaffoldingModelFactory.VisitDatabaseModel(ModelBuilder modelBuilder, DatabaseModel databaseModel)
   at IModel Microsoft.EntityFrameworkCore.Scaffolding.Internal.RelationalScaffoldingModelFactory.Create(DatabaseModel databaseModel, ModelReverseEngineerOptions options)

EF Core version: 5, 6
Database provider: often Microsoft.EntityFrameworkCore.SqlServer

[ErikEJ]

@AndriySvyryd @ajcvickers What solution are you proposing - maybe I could do a PR?

[AndriySvyryd]

Ignoring the second FK and logging a warning would be acceptable.