无法将值NULL插入“ BaslikId”列中

Question

I want to have a relationship on my tables. I take this error when I update db.

Cannot insert the value NULL into column 'BaslikId', table 'BlogSitesi.dbo.Konular'; column does not allow nulls. UPDATE fails.
The statement has been terminated.

My Models :

public abstract class BaseModel
{
    public int id { get; set; }
}


public class Baslik:BaseModel
{
    public string Ad { get; set; }
    public int KonuAdet { get; set; }

    public virtual List<Konu> Konular { get; set;}
}


public class Konu:BaseModel
{
    public string KonuBaslik { get; set; } 
    public string Icerik { get; set; }
    public int BaslikId { get; set; }

    public virtual Baslik Baslik { get; set; }
}

I want to create a relation between Konu and Baslik (1-n Relation).

How can I fix this?

Answer 1

It seems that you are looking for a 0-n relationship between Konu and Baslik:

modelBuilder.Entity<Konu>()
        .HasOptional(s => s.Baslik)
        .WithMany(g => g.Konu)
        .HasForeignKey(s => s.BaslikId);

Also, you need to specify your fk as int? to make it nullable like the following:

public int? BaslikId { get; set; }

Answer 2

Hi I think that you have set column property in your database to "NOT NULL" which means that the database will not allow you to insert NULL values to this column. It's basic practice that id column should be set to NOT NULL. Why you want to insert NULL to id column in first place? This will make trouble when you will do joins.