EF Core table with only foreign key

Question

I have this situation:

The second table is not inheriting the first one. It will contain different information

I'm using EF Core and I've trouble configuring the models for the two entities. I work with fluent API configurations and using EF Core Migrations to create the tables. The models and their configurations are as follows:

public class Table1 
{
    public long Id { get; set; }
    public string FirstName { get; set; }

    public List<Table2> T2 { get; set; }
}

public class Table1Configuration : IEntityTypeConfiguration<Table1>
{
    public void Configure(EntityTypeBuilder<Table1> builder)
    {
        builder.ToTable("table1");

        builder.Property(s => s.Id)
            .HasColumnName("id")
            .HasColumnType("serial");

        builder.Property(s => s.FirstName)
            .HasColumnName("first_name");
    }
}

The second one:

public class Table2 
{
    public long Table1Id { get; set; }
    public DateTime Timestamp { get; set; }
    public double Value { get; set; }

    public Table1 T1 { get; set; }

}

public class Table2Configuration : IEntityTypeConfiguration<Table2>
{
    public void Configure(EntityTypeBuilder<Table2> builder)
    {
        builder.ToTable("table2");

        builder.Property(s => s.Table1Id)
            .HasColumnName("table1_id");
        builder.HasNoKey();

        builder.Property(s => s.Timestamp)
            .HasColumnName("ts");

        builder.Property(s => s.Value)
            .HasColumnName("value");

        builder.HasOne(s => s.T1)
            .WithMany(s => s.T2)
            .HasForeignKey(s => s.Table1Id);
    }
}

When I run the Update-Database command it throws exception:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
System.InvalidOperationException: The navigation '' cannot be added because it targets the keyless entity type 'Table2'. Navigations can only target entity types with keys.

How can we have a table with only foreign keys? I do not want to put an extra column for a primary key, because the second table will be flushed frequently

If I miss some information that will be helpful, please ask me to include in in the comments!

Thanks in advance, Julian

Answer 1

As anybody stumbles the same problem, as @Bryan Lewis suggested in the comment, I've just added a primary key to the table