Dim qry = _
 From r In iprolensrange _
 From t In iprolenstype _
 Where r.hst_code_grundglas = t.hst_code_grundglas _
 And CDate(IIf(t.Islieferbar_abNull, currentDate, t.lieferbar_ab)) < _
 currentDate _
 And CDate(IIf(t.Islieferbar_bisNull, currentDate, t.lieferbar_bis)) > _
 currentDate _
 Group By k = New With {t.ein_mehrstärken, r.hst_code_grundglas} Into grp = _
 Group _
 From g In grp _
 Order By g.t.ein_mehrstärken, g.r.hst_code_grundglas _
 Select g.t.standard_marke, g.r.hst_code_grundglas

AndAlso (t.Islieferbar_abNull() OrElse t.lieferbar_ab < currentDate)