What's wrong with Entity Framework Core?

Question

ASP.NET

Good day, dear ones. Help. Everything worked fine, but an error like
"SqlException: Cannot insert an explicit value for the identity column in the table "Deals" when the IDENTITY_INSERT parameter is set to OFF began to pop up.
"
I noticed that the ID of the object has a minimum value of int32. In doing so, I pre-set it to zero.

for (int k =0; k < deals1.Length; k++) {
                                deals1[k].ParentDealID = db.Deals.Where(d => d.GUID == parentDealInfo.GUID).FirstOrDefault().DealID;
                                deals1[k].DealID = 0;
                                Console.WriteLine(JsonConvert.SerializeObject(deals1[k]));
                                Console.WriteLine("Сделка: {0}; ParentDeal: {1}", deals1[k].ChildNumber, deals1[k].ParentDealID);
                                db.Add(deals1[k]);
                                db.SaveChanges();
                                Thread.Sleep(5);
                            }

Or maybe I'm missing something in the indexes. If I didn't explicitly set it, then it should sort of install itself, and EFCore seems to take care of it.

Answer 1

This happens when the DealID is manually changed to an entry that is already in the database.
Where did deals1 come from ? Sampling from a database context? If yes, then EntityFramework knows that these records are already in the database and tracks their changes. Accordingly, it does not allow changing their identifiers explicitly and overwriting them in the database again.