arrow_back Where is the violation of the foreign key?

Question

There is a table in the database, it has a tree of objects. When I try to add a record it gives out "violation of foreign key constraints". When you add manually, everything is fine.

Part of the model

public int? ParentId { get; set; }
 public Good Parent { get; set; }
 public virtual ICollection<Good> LinkedGoods { get; set; }

builder.Entity<Good>().HasOne(x => x.Parent).WithMany(x => x.LinkedGoods).HasForeignKey(x => x.ParentId).OnDelete(DeleteBehavior.SetNull);

First I create the main object, save it and pass here its Id and the number of child products

private async Task<OkResult> CreateLinkedItems(int parentId,int linkQuantity)
        {
            var good = await _db.Goods.FindAsync(parentId);
            good.Id = 0;
            for (int i = 0; i < linkQuantity; i++)
            {
                (var code, var number) = GetCode(good.CategoryId, good.HasDefects);
                
                 good.Code = code;
                 good.Number = number;
                good.ParentId = good.Id;
               
                _db.Goods.Add(good);
                _db.SaveChanges();
            }
            return Ok();
        }

P.S Checked the data manually, the error is in ParentId

Answer 1

The problem was that the DbContext was tracking this object. And there are two ways of solving AsNoTraking() or manually prescribing the creation of a new object

Answer 2

In principle, the for code is strange - i inside the loop is not used.
Something must be created in the loop, but so far it is not.

good.Id = 0, and then good.ParentId = good.Id; ParentId definitely cannot be set to 0, since there can be no such id.

Apparently you need to create a new goodNew inside the for loop and work with it inside the loop, e.g. goodNew.ParentId = good.Id

Comments

ParentId refers to another record