TCriteria and testing for ''

I can?t get this to work:

This works ok:

I want to test for empty strings additionally:
Criteria.Add(Linq.IsNotNull('LebensmittelCD') and (Linq['LebensmittelCD'] <> ''));
as well as this
Criteria.Add(not Linq.Eq('LebensmittelCD',''));

does not return any rows - but should return 5.

The trace Shows (have alook at the missing Operator!!):
[23.10.2019 15:46:00][Trace][Value: SELECT A.ID AS A_ID, A.IDExtern AS A_IDExtern, A.BezeichnungExtern AS A_BezeichnungExtern, A.HerkunftCD AS A_HerkunftCD, A.LebensmittelCD AS A_LebensmittelCD, A.Bezeichnung AS A_Bezeichnung
WHERE  A.BezeichnungExtern LIKE :p_0 AND
(A.LebensmittelCD Is Not Null And A.LebensmittelCD  :p_1)][Type: string]
Prozess RezeptSchnittstelle.exe (6424)
Debug-Ausgabe: [23.10.2019 15:46:00][Trace][Value: p_0 = "%%" (ftString)][Type: string] Prozess RezeptSchnittstelle.exe (6424)
Debug-Ausgabe: [23.10.2019 15:46:00][Trace][Value: p_1 = "" (ftString)][Type: string] Prozess RezeptSchnittstelle.exe (6424)
The missing operator is a quirk in the logger, so that is not the problem.
If I compare against a blank instead of an empty string, the result is ok.
If I execute the query in Management Studio (even with Parameters) the result is ok.

What does this mean?
Instead of
Criteria.Add(Linq.IsNotNull('LebensmittelCD') and (Linq['LebensmittelCD'] <> ''));
this one
Criteria.Add(Linq.IsNotNull('LebensmittelCD') and (Linq['LebensmittelCD'] <> ' '));

BTW: Criteria.Add(Linq.IsNotNull('LebensmittelCD') and (Linq['LebensmittelCD'].Len > 0 ));
works too.

I cannot reproduce the problem, can you please provide more details? 

Maybe a sample project that reproduces the issue? 
What database are you using? Which version?
What component are you using to connect to the database?

Isn't this the same problem with old SQL Server driver?

No, this is the new driver.

Can you please provide a project via e-mail that reproduces the problem? It depends on data in the database as well.