EF Query pulls null when dbase shows populated field - entity-framework

Question

I've got an issue with EF Core in which I loop through a list of objects and create related elements in another list. As I process the first object everything is great, it is added to the list properly and looks great when we pull the information from the database.
At the start of the code for processing each object, I grab more detailed information from the database about that object (it's related objects and such). When the query executes for the second object information in another object changes. It changes a foreign key to be null for the first object instead of the proper value. If I look in the database as that occurs, the foreign key is set properly. This change in the foreign key shown in the query causes it to show as dirty in the context.
Therefore, when we finish processing the second object and make an update to the database, the system commits the (now) null foreign key to the database. This causes all sorts of issues, as you would expect.
partial object definition below
public partial class CommandType
{
public int? FkATSId { get; set; }
public virtual ATST FkATS { get; set; }
}
public partial class ATST
{
public virtual ICollection<FAT> FAT{ get; set; }
}
public partial class FAT
{
public int? FkDTRTId{ get; set; }
public virtual DTRT FkDTRT { get; set; }
}
public partial class DTRT
{
public int? FkFDTid{ get; set; }
public virtual FDT FkFDT{ get; set; }
}
public partial class FDT
{
...
}
The value that gets comes back as a change to null is FkFDTid in the DTRT.
if we are processing 5 of the items, 4 will end up with a null id and the last one will have the proper foreign key. If we processed 10, 9 would have the bad id and the last one would be good.
If I go through the code in the debugger and keep an eye on the context directly, the value does not come back from the query as null and so things work fine. But, only if I keep the context open in the locals tab of VS.
Does anyone have any ideas?

Answer 1

It turns out the issue was a discrepancy between the database and the entity framework context. The database for one of the items had the foreign key as not unique, but the context, for some reason, had it as unique.
We were able to store values into the database but if we queried the database and brought more than one record that had the same foreign key value, EF would think to itself: This can't be, that foreign key must be unique. I'll set the first one I grabbed to be null. Voila, they're not unique. Oh, because I changed that foreign key, the record is now dirty and will be committed to the database when we do a save changes.
The takeaway from this: if you see values that are different from what is stored in the database after you query the database, check foreign key and uniqueness constraints.