EFCore generates phantom column name in select

Question

I am upgrading a project to EFCore 2.2.0 from 2.1.3 and encountered this bizarre issue. When loading data for a simple table, I get an exception that 'ExchangeCd1' is not defined. This column does not exist, but it is not referenced anywhere in the code. When I examine the mapping properties, I see it is listed as: {Property: ExchangeHoliday.ExchangeCd1 (no field, string) Shadow FK Index 2 2 2 0 1}

The classes are pretty simple, but the child has a composite primary key and the parent tries to reference it using its individual key.

public class Exchange
{
    public string ExchangeCd { get; set; }

    public string ExchangeName { get; set; }

    public DayOfWeek WeekendStart { get; set; }

    public DayOfWeek WeekendEnd { get; set; }

    public ICollection<ExchangeHoliday> Holidays { get; set; }
}

public class ExchangeHoliday
{
    public string ExchangeCd { get; set; }

    public DateTime HolidayDate { get; set; }

    public bool IsTradeHoliday { get; set; }

    public bool IsSettleHoliday { get; set; }
}

I add some mapping, in order to define the primary key as a composite key

modelBuilder.Entity<Exchange>().HasKey(e => e.ExchangeCd);
modelBuilder.Entity<ExchangeHoliday>().HasKey(e => new { e.ExchangeCd, e.HolidayDate });

Then I execute a very simple select

var holidays = await dbContext.ExchangeHolidays.ToArrayAsync(cancellationToken).ConfigureAwait(false);

I turned on EFCore SQL logging, and it generates this for the SQL

SELECT [e].[exchange_cd], [e].[holiday_date], [e].[ExchangeCd1], [e].[is_settle_holiday], [e].[is_trade_holiday]
FROM [exchange_holiday] AS [e]

I tried to add explicit mapping to remove the shadow key, but it sticks around

modelBuilder.Entity<Exchange>()
                    .HasMany<ExchangeHoliday>()
                    .WithOne(e => e.Exchange)
                    .HasForeignKey(fk => fk.ExchangeCd);

Answer 1

Ok, so if I do the mapping on the child, it resolves the issue

modelBuilder.Entity<ExchangeHoliday>()
                    .HasOne<Exchange>()
                    .WithMany(e => e.Holidays)
                    .HasForeignKey(e => e.ExchangeCd);