Cloning entity with EF 6, null reference exception

Question

I am trying to clone an entity (EF 6.x, code first), using the technique here: Entity Framework 5 deep copy/clone of an entity However, I get a strange NullReference exception when trying to add the cloned ticket to the DbSet: ``` var clonedTicket = _context.Tickets .AsNoTracking() .Include(o => o.Lines.Select(l => l.Serials)) .Include(o => o.Payments.Select(p => p.PayCodeInfo)) .SingleOrDefault(o => o.TicketId == ticketId); clonedTicket.TicketId = _context.Tickets.Max(o => o.TicketId) + 1; foreach (var line in clonedTicket.Lines) line.TicketId = clonedTicket.TicketId; foreach (var payment in clonedTicket.Payments) payment.TicketId = clonedTicket.TicketId; _context.Tickets.Add(clonedTicket); <---- System.NullReferenceException _context.SaveChanges(); ``` The exception is on _context.Tickets.Add(clonedTicket). clonedTicket looks perfectly normal, nothing is null that should not be. Of course, both _context and Tickets (the DbSet) are non-null. Here is the full exception: ``` System.Nul…

Accepted Answer

I got this working. The trick was to set ProxyCreationEnabled = false before retrieving the entity:

```
_context.Configuration.ProxyCreationEnabled = false;
var returnTicket = _context.Tickets
   .AsNoTracking()
   .Include(o => o.Lines.Select(l => l.Serials))
   .Include(o => o.Payments)
   .SingleOrDefault(o => o.TicketId == ticketId);
_context.Configuration.ProxyCreationEnabled = true;
```

I cannot say that I fully understand why this is, but I guess it has to do with the lazy loading that EF does when ProxyCreation is enabled (which I do not need/want here, since I am loading the related entities explicitly).

Cloning entity with EF 6, null reference exception

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