UseDatabaseNullSemantics still generating NULL checks

Question

I have this on my context object (constructor):

this.Configuration.UseDatabaseNullSemantics = true;

But even with this set, this query:

Answer 1

Does this work? If the posted query is correct when you remove the (or (is null and is null)) clause, then I think this will execute the same query. (This assumes there isn't a logic error in the joins, as suggested in other posts.)

var query = (from i in _repo.Invoices
    from o in _repo.Orders.Where(c => c.orderid == i.orderid)
    from o2 in _repo.Orders.Where(c => c.linkedorderid == o.linkedorderid).DefaultIfEmpty()                          
    where invoiceIds.Contains(i.invoiceid)
    select new
    {
       i, o2
    }).ToList();

Answer 2

The condition you see inside the generated SQL has nothing in common with UseDatabaseNullSemantics and is needed to handle correctly LEFT LOINs with nullable keys.

I think the problem you are experiencing is caused by a logical error in your query. IMO, the join condition

on o.linkedorderid equals o2.linkedorderid

should be

on o.linkedorderid equals o2.orderid

because normally the FK relates (joins) to the PK.