EF-1：1关系不在主键上

Question

I want to create an optional 1:1 mapping between two existing (legacy) tables where each MainTable record may or may not have - at most - one SubTable record:

internal class MainTable
{
    [Key]
    public int Id { get; set; }
}
internal class SubTable
{
    [Key]
    public int Id { get; set; }
    public int MainTableId { get; set; }
}

The SubTable.Id does not really serve any purpose but preferably it remains the PrimaryKey and AutoGenerated because of legacy code still running.

OnModelCreating gets updated with:

modelBuilder.Entity<MainTable>()
    .HasOptional(x => x.Sub)
    .WithRequired(x => x.Main);

With the above Models, I run Add-Migration initial and Update-Database . I then update the models to:

internal class MainTable
{
    [Key]
    public int Id { get; set; }
    public SubTable Sub { get; set; } // new
}
internal class SubTable
{
    [Key]
    public int Id { get; set; }
    public int MainTableId { get; set; }
    public MainTable Main { get; set; } // new
}

Running Add-Migration creates a new one but running it gives the following error: Table 'dbo.SubTable' doesn't exist

The generated migration:

public override void Up()
{
    DropPrimaryKey("dbo.SubTable");
    AlterColumn("dbo.SubTable", "Id", c => c.Int(nullable: false));
    AddPrimaryKey("dbo.SubTable", "Id");
    CreateIndex("dbo.SubTable", "Id");
    AddForeignKey("dbo.SubTable", "Id", "dbo.MainTable", "Id");
}

I'm unsure why EF wants to drop all primary keys etc but the last line seems to suggest that it wants to bind Sub.Id->Main.Id while it should bind Sub.MainTableId->Main.Id.

After that I've tried messing with DataAnnotationAttributes instead [ForeignKey] , [Index("name", 1, IsUnique = true)] etc but to no avail.

Answer 1

Ill do something like this

internal class MainTable
{
    [Key]
    public int Id { get; set; }

    public virtual SubTable Sub { get; set; } // new
}
internal class SubTable
{
    [Key]
    public int Id { get; set; }
    public int MainTableId { get; set; }

    [ForeignKey("MainTableId")]
    public virtual MainTable Main { get; set; } // new
}