ASP NET MVC Core 2 with entity framework saving primery key Id to column that isnt a relationship column - foreign-keys

Question

Please look at this case:
if (product.ProductId == 0)
{
product.CreateDate = DateTime.UtcNow;
product.EditDate = DateTime.UtcNow;
context.Products.Add(product);
if (!string.IsNullOrEmpty(product.ProductValueProduct)) { SaveProductValueProduct(product); }
}
context.SaveChanges();
When I debug code the ProductId is negative, but afer save the ProductId is corect in database (I know this is normal), but when I want to use it here: SaveProductValueProduct(product) after add to context.Products.Add(product); ProductId behaves strangely. (I'm creating List inside SaveProductValueProduct)
List<ProductValueProductHelper> pvpListToSave = new List<ProductValueProductHelper>();
foreach (var item in dProductValueToSave)
{
ProductValueProductHelper pvp = new ProductValueProductHelper();
pvp.ProductId = (item.Value.HasValue ? item.Value : product.ProductId).GetValueOrDefault();
pvp.ValueId = Convert.ToInt32(item.Key.Remove(item.Key.IndexOf(",")));
pvp.ParentProductId = (item.Value.HasValue ? product.ProductId : item.Value);
pvpListToSave.Add(pvp);
}
I want to use ProductId for relationship. Depends on logic I have to save ProductId at ProductId column OR ProductId at ParentProductId column.
The ProductId 45 save corent at ProductId column (3rd row - this is a relationship), BUT not at ParentProductId (2nd row - this is just null able int column for app logic), although while debug I pass the same negative value from product.ProductId there.
QUESTION:
how can I pass correct ProductId to column that it isn't a relationship column

Answer 1

I just use SaveProductValueProduct(product) after SaveChanges (used SaveChanges twice)
if (product.ProductId == 0)
{
product.CreateDate = DateTime.UtcNow;
product.EditDate = DateTime.UtcNow;
context.Products.Add(product);
}
context.SaveChanges();
if (product.ProductId != 0)
{
if (!string.IsNullOrEmpty(product.ProductValueProduct)) { SaveProductValueProduct(product); }
context.SaveChanges();
}
I set this as an answer because it fixes the matter, but I am very curious if there is any other way to solve this problem. I dont like to use context.SaveChanges(); one after another.