title: Object reference not set to an instance of an object - specific
body: <p>Why do I have this this error? - "Object reference not set to an instance of an object?"
  This is application which connects to the SubiektGT database. Subiekt is a sales system. I know there is so many topics like this but I can't find a solution for thais one.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>Public Class SubiektGT
  
      Dim gt As New InsERT.GT
      Dim daneKlienta As New SklepPobieranieDanych  
  
      'Connection to Subiekt database
      Function UruchomSubiekta() As InsERT.Subiekt
  
          Dim oSgt As InsERT.Subiekt
  
          Try
              gt.Produkt = InsERT.ProduktEnum.gtaProduktSubiekt
              gt.Serwer = "USER-KOMPUTER\insertgt"
              gt.Baza = "Sklep"
              gt.Autentykacja = InsERT.AutentykacjaEnum.gtaAutentykacjaMieszana
              gt.Uzytkownik = ""
              gt.UzytkownikHaslo = ""
              gt.Operator = "Szef"
              gt.OperatorHaslo = ""
  
              oSgt = gt.Uruchom(InsERT.UruchomDopasujEnum.gtaUruchomDopasuj, InsERT.UruchomEnum.gtaUruchomWTle)
  
          Catch ex As Exception
              MessageBox.Show("Błąd: " &amp; ex.Message)
          End Try    
      End Function
  
  
      Private Sub btnDodajKlientaDoSubiekta_Click(sender As Object, e As EventArgs) Handles btnDodajKlientaDoSubiekta.Click    
          daneKlienta.PobierzDaneKlientaDlaSubiekt()
          DodajKontrahenta()   
      End Sub
  
  End Class
  </code></pre>
  
  <p>Here is the code which throws that exception:</p>
  
  <pre><code>Public Sub DodajKontrahenta()
  
              Dim oSgt As InsERT.Subiekt
              Dim oKh As InsERT.Kontrahent
  
              oSgt = UruchomSubiekta()
  
              oKh = oSgt.Kontrahenci.Dodaj  'EXCEPTION
              oKh.Typ = InsERT.KontrahentTypEnum.gtaKontrahentTypDostOdb
  
              oKh.Nazwa = daneKlienta.Nazwa
              oKh.NazwaPelna = daneKlienta.Nazwa
              oKh.Miejscowosc = daneKlienta.Miejscowosc
              oKh.Ulica = daneKlienta.Adres
              oKh.Email = daneKlienta.Email
  
              oKh.Zapisz()
              oKh.Zamknij()
          End Sub
  </code></pre>
  
  <p><code>InsERT.Kontrahent</code> is an interface and when the exception comes I try to create a new object. A really don't know why.</p>