What exactly does PreserveReferences do to compare objects?

[OronDF343]

My scenario (simplified):

public class MessageViewModel
{
    public List<RecipientViewModel> EmailRecipients { get; set; }
    public List<RecipientViewModel> SmsRecipients { get; set; }
}

public class Message
{
    public List<Recipient> EmailRecipients { get; set; }
    public List<Recipient> SmsRecipients { get; set; }
}

The goal is to map from MessageViewModel to Message.
EmailRecipients and SmsRecipients may contain items that are in fact the same reference.
Recipient implements Equals and GetHashCode, while RecipientViewModel does not.
The documentation says almost nothing about PreserveReferences.

1. I should call PreserveReferences() on my mapping from RecipientViewModel to Recipient, correct?
2. PreserveReferences uses GetHashCode? #3654 implies that PreserveReferences uses GetHashCode.
   Does this mean that true reference equality is preserved only if the source type does not implement GetHashCode?
3. What happens if I reverse the mapping?

[lbargaoanu]

I suggest that you write some tests to answer your questions. You can also check our tests for PreserveReferences.
Also, check the execution plan.