具有级联更新和删除的同一个表的多个外键

Question

I'm trying to add multiple foreign keys for one entity that will be connected to same other table with cascade update and delete.

So I have Series and Argument entity:

public class Series : Entity<int>
{
    public string Name { get; set; }
    public int IterationsId { get; set; }
    public int KId { get; set; }
    public int LambdaId { get; set; }
    public int GradientId { get; set; }
    public int ImproveId { get; set; }
    public int TrainingId { get; set; }
    public DateTime CreateDateTime { get; set; }
    public DateTime? ChangeDateTime { get; set; }
    public virtual Argument Iterations { get; set; }
    public virtual Argument K { get; set; }
    public virtual Argument Lambda { get; set; }
    public virtual Argument Gradient { get; set; }
    public virtual Argument Improve { get; set; }
    public virtual Argument Training { get; set; }
}

public class Argument : Entity<int>
{
    public Argument()
    {
        Values = new List<ArgumentValue>();
    }

    public int Min { get; set; }
    public int Max { get; set; }
    public int Step { get; set; }
    public ArgumentType ArgumentType { get; set; }
    public virtual ICollection<ArgumentValue> Values { get; set; }
}

With theirs mappings:

public class SeriesMap : BaseMap<Series, int>
{
    public SeriesMap()
    {
        ToTable("Series");

        Property(x => x.Name).IsRequired();
        Property(x => x.CreateDateTime).IsRequired();
        Property(x => x.ChangeDateTime).IsOptional();

        HasRequired(x => x.Iterations).WithMany().HasForeignKey(x => x.IterationsId).WillCascadeOnDelete(true);
        HasRequired(x => x.K).WithMany().HasForeignKey(x => x.KId).WillCascadeOnDelete(true);
        HasRequired(x => x.Lambda).WithMany().HasForeignKey(x => x.LambdaId).WillCascadeOnDelete(true);
        HasRequired(x => x.Gradient).WithMany().HasForeignKey(x => x.GradientId).WillCascadeOnDelete(true);
        HasRequired(x => x.Improve).WithMany().HasForeignKey(x => x.ImproveId).WillCascadeOnDelete(true);
        HasRequired(x => x.Training).WithMany().HasForeignKey(x => x.TrainingId).WillCascadeOnDelete(true);
    }
}

public class ArgumentMap : BaseMap<Argument, int>
{
    public ArgumentMap()
    {
        ToTable("Argument");

        Property(x => x.Min).IsRequired();
        Property(x => x.Max).IsRequired();
        Property(x => x.Step).IsRequired();

        HasMany(x => x.Values);
    }
}

But when I try to create such a model I have a exception with message:

Introducing FOREIGN KEY constraint 'FK_dbo.Series_dbo.Argument_ImproveId' on table 'Series' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

When I change

.WillCascadeOnDelete(true);

to

.WillCascadeOnDelete(false);

model creates but not as I want to. Is it somehow possible to have muplite references to same table with cascade update/delete?

Answer 1

Basically, SQL Server does not allow creating cascade actions on Inner relationships – when the cascade path goes from column col1 in table A to column col2 also in table A (A => A).

Therefore the only way to enforce cascade delete for this relationships is to use SQL-Triggers directly on the SQL-Database or iterate the collection and remove all children objects.

Hope it helps!