EF4 mapping one-to-many

Question

Please help to find the error.

Error text: One or more validation errors were detected during model generation. Because all of the properties in the dependent role are non-nullable, multiplicity of the principal role must be 1.

//File.cs
public class File
{
   public int Id { get; set; }
   public string Name { get; set; }

   public ICollection<Sp> Sps { get; set; }
}
//Sp.cs
public class Sp
{
   public int Id { get; set; }
   public int FileId { get; set; }
   public File File { get; set; }
}

mapping code

//mapping File
class File :  EntityTypeConfiguration<File>
{
    public File()
    {
        ToTable("File", "dbo");
        HasKey(x => x.Id);

        Property(x => x.Id).HasColumnName("ID");
        Property(x => x.Name).HasColumnName("NAME");
    }
}
//mapping Sp
class Sp :  EntityTypeConfiguration<Sp>
{
   public Sp()
   {
      ToTable("Sp", "dbo");
      HasKey(x => x.Id);

      Property(x => x.Id).HasColumnName("ID");
      Property(x => x.FileId).HasColumnName("FILE_ID");

      //the location of the error
      HasOptional(d => d.File)
        .WithMany(d => d.Sps)
        .HasForeingKey(d => d.FileId)
        .WillCascadeOnDelete(false);
    }
 }

Answer 1

You have an optional foreign key mapped to a non nullable property which is contradictory, you need to go one way or the other.

Change HasOptional to HasRequired which means every Sp must have an associated File .

class Sp :  EntityTypeConfiguration<Sp>
{
   public Sp()
   {
      ToTable("Sp", "dbo");
      HasKey(x => x.Id);

      Property(x => x.Id).HasColumnName("ID");
      Property(x => x.FileId).HasColumnName("FILE_ID");

      //the location of the error
      HasRequired(d => d.File)
        .WithMany(d => d.Sps)
        .HasForeingKey(d => d.FileId)
        .WillCascadeOnDelete(false);
    }
 }

If this is not what you want then make FileID nullable

public class Sp
{
   public int Id { get; set; }
   public int? FileId { get; set; }
   public File File { get; set; }
}

Which will allow you to have Sp records with no associated File .