OnDelete restrict doesn't allow me delete an entity

[ComptonAlvaro]

I have two entities, one parent entity and one child entity. The relationship between both are this:

entity.HasOne(d => d.EntityParent)
    .WithMany(p => p.EntityCHild)
    .HasForeignKey(d => d.IDEntityParent)
    .OnDelete(DeleteBehavior.restrict)
    .HasConstraintName("FK_Name");

But when I try to delete the parent entity I get an error that says that I can't delete the parent entity because it doesn't allow to set null values. I have to configure the OnDelete if I want to delete the parent entity. If I set on cascade, then I don't have problems or I can delete OnDelete configuration and it works too.

In my database, I have configurated the foreign key in the child table that doesn't allow null value, so it is coherent the message error that I receive.

In my database, I don't have child entities, so how I could delete the parent entity? Really the strict configuartion is the correct one, because the foreign key in the child doesn't allow null values, so I guess that the correct configuration is restric, but If I set this configuration, I can't delete the parent entity when it has not childs.

This is the expected behavior? Because it is, I don't know how I can delete the parent entity, because if I execute the query directly in the database I will not get errors because it has not childs, but EF doesn't allow me because of this error.

thanks.

EDIT: I get this error:

"The association between entity types 'MyTypeParent' and 'MyTypeChild' has been severed but the foreign key for this relationship cannot be set to null. If the dependent entity should be deleted, then setup the relationship to use cascade deletes."

The relationship is configurated as restrict. According to the documentation:

"The delete operation is not applied to dependent entities. The dependent entities remain unchanged."

So if the dependent entities remain unchanged, the foreign key still is the same that they had, so it shouldn't be changed to null, that seems the meaning of the error. If not, what is the difference between set null and restrict?

If I set OnDelete as setNull, I get this error:

"The association between entity types 'myEntityparent' and 'MyEntityChild' has been severed but the foreign key for this relationship cannot be set to null. If the dependent entity should be deleted, then setup the relationship to use cascade deletes."

Is the same message error, so what is the difference between restrict and setNull?

Thanks.

[ajcvickers]

@ComptonAlvaro Agree the documentation is confusing. We will take a look at making it better.

You should have no trouble deleting a parent entity if it has no children. If the parent entity does have children, and the FK is non-nullable, then deleting the parent will cause an error because the constraint on the children means that they cannot continue to exist without the parent. This is the same as for an FK constraint in the database. If you want the children to continue to exist without the parent, then the FK property must be nullable such that a child can exist without referencing a parent.

[ComptonAlvaro]

I understand that. But in my case, if I set restrict and I get all the childs from database, if I delete the childs in the dbContext and the parent too, I get this error. It is true that the database doesn't allow null values in the relationship, but I get all the childs from database and I delete them. So why I get this error? EF should allows to delete them, and if a new child is add while I am deleting them then the error should come from database, not from EF.

Also, the message error that gives EF is not very clear, because in strict and in setNull configurations, I get the same message error. Why EF try to set to null the FK if according to documentation restrict will not change any value?

[ajcvickers]

@ComptonAlvaro With regard to, " I get all the childs from database, if I delete the childs in the dbContext and the parent too, I get this error." I am not able to reproduce this. If I mark the parent and all the children as deleted, then EF will delete them all. Here is the code I used to try to reproduce what you are seeing. Maybe you can look at this and try to see what is different from your case?

public class Program
{
    public static void Main()
    {
        using (var context = new BlogContext())
        {
            context.Database.EnsureDeleted();
            context.Database.EnsureCreated();

            context.Add(new Blog { Posts = new List<Post> { new Post(), new Post(), new Post() } });
            context.SaveChanges();
        }

        using (var context = new BlogContext())
        {
            var blog = context.Blogs.Include(e => e.Posts).FirstOrDefault();

            context.RemoveRange(blog.Posts);
            context.Remove(blog);
            context.SaveChanges();
        }
    }
}

public class Blog
{
    public int Id { get; set; }
    public ICollection<Post> Posts { get; set; }
}

public class Post
{
    public int Id { get; set; }
    public int BlogId { get; set; }
    public Blog Blog { get; set; }
}

public class BlogContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(
            "Server=(localdb)\\mssqllocaldb;Database=TestDB;Trusted_Connection=True;MultipleActiveResultSets=true;ConnectRetryCount=0");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Post>().HasOne(d => d.Blog)
            .WithMany(p => p.Posts)
            .HasForeignKey(d => d.BlogId)
            .OnDelete(DeleteBehavior.Restrict)
            .HasConstraintName("FK_Name");
    }
}

[ajcvickers]

@ComptonAlvaro Agree that the documentation is confusing. At runtime, EF doesn't really treat Restrict and SetNull differently.

Note for triage: this is the enum we have, which is used directly by the OnDelete method in Code First:

/// <summary>
///     Indicates how a delete operation is applied to dependent entities in a relationship when the principal is deleted
///     or the relationship is severed.
/// </summary>
public enum DeleteBehavior
{
    /// <summary>
    ///     The delete operation is not applied to dependent entities. The dependent entities remain unchanged.
    /// </summary>
    Restrict,

    /// <summary>
    ///     The foreign key properties in dependent entities are set to null. This cascading behavior is only applied
    ///     to entities that are being tracked by the context. A corresponding cascade behavior should be setup in the
    ///     database to ensure data that is not being tracked by the context has the same action applied. If you use
    ///     EF to create the database, this cascade behavior will be setup for you.
    /// </summary>
    SetNull,

    /// <summary>
    ///     Dependent entities are also deleted. This cascading behavior is only applied
    ///     to entities that are being tracked by the context. A corresponding cascade behavior should be setup in the
    ///     database to ensure data that is not being tracked by the context has the same action applied. If you use
    ///     EF to create the database, this cascade behavior will be setup for you.
    /// </summary>
    Cascade
}

[ComptonAlvaro]

Well, i found the problem. In my case I was using raw sql with the fromSql() method, and also i was doing the incluide, but in my t-sql query I didn't get the childs, so EF knows that I have not childs although I was doing the include. When I add the childs in the t-sql it works.

So it was my problem.

Thank you so much.

[ajcvickers]

Discussed in triage to leave API unchanged but update docs to clarify that Restrict and SetNull have the same behavior for tracked entities.

[ajcvickers]

Note: See other documentation issues noted in #8485

[ajcvickers]

Superceeded by #8654