Xtykutl

I had this:

public class Customer

{

    public int Id {get; set;}

    //some more properties

}



public class Payment

{

    public int Id {get; set;}

    public int CustomerId {get; set;} //foreign key

    public Customer Customer {get; set;}

}

Which lead to a foreign key constraint in the database. Then I made the CustomerId nullable:

public class Payment

{

    public int Id {get; set;}

    public int? CustomerId {get; set;} //foreign key

    public Customer Customer {get; set;}

}

If I generate the migration script, I get something like this:

IF NOT EXISTS(SELECT * FROM [__EFMigrationsHistory] WHERE [MigrationId] = N'MyMigration')

BEGIN



DECLARE @var2 sysname;



    SELECT @var2 = [d].[name]

      FROM [sys].[default_constraints] [d]

INNER JOIN [sys].[columns] [c] ON [d].[parent_column_id] = [c].[column_id] 

       AND [d].[parent_object_id] = [c].[object_id]

     WHERE ([d].[parent_object_id] = OBJECT_ID(N'[Payments]') AND [c].[name] = N'CustomerId');



IF @var2 IS NOT NULL EXEC(N'ALTER TABLE [Payments] 

    DROP CONSTRAINT [' + @var2 + '];');



ALTER TABLE [Payments] ALTER COLUMN [CustomerId] int NULL;

END;



GO

So now column Payments.CustomerId is nullable, but the foreign key constraint is removed. How can I get the foreign key constraint back?

edit: One more thing. Between my code changes, I also added this in protected override void OnModelCreating(ModelBuilder modelBuilder):

new PaymentMap(modelBuilder.Entity<Payment>());

You need to annotate it with System.ComponentModel.DataAnnotations.Schema.ForeignKeyAttribute explicitly:

public class Payment

{

    public int Id {get; set;}



    public int? CustomerId {get; set;} //foreign key



    [ForeignKey("CustomerId")]

    public Customer Customer {get; set;}

}

In order to make it work you should add public virtual ICollection<Tenant> Payments { get; set;} to Customer class

Blockquote

public class Customer

{

    public int Id { get; set; }

    public virtual ICollection<Payment> Payments { get; set; }

}



public class Payment

{

    public int PaymentId{ get; set; }

    public int? CustomerId { get; set; }

    public Customer Customer { get; set; }

}

As EF Core requires manually making the connections between tables, have you tried to write them down in your DataContext class?

Add List<Payment> Payments in your Customer class and in your DataContext class in the OnModelCreate override method add:

builder

     .Entity<Payment>()

     .HasOne(p => p.Customer)

     .WithMany(c => c.Payments)

     .HasForeignKey(p => p.CustomerId);

I dropped my local database and re-created it with "update-database". That solved my problem. Thanks everybody for their time and effort!