Dim res = (From patienten In patient_list Join bh_status In bh_status_list _
          On patienten.beihilfe_id Equals bh_status.beihilfe_id _
          Select patienten.patient_id, patienten.patient_vorname, _
          patienten.patient_nachname, _
          patienten.patient_geburtsdatum, patienten.beihilfe_id, _
          patienten.beihilfesatz).ToList

For Each patient In res
            Dim patienten_node As New TreeNode
            patienten_node.Tag = patient
            patienten_node.Text = patient.patient_vorname
            patientnode.Nodes.Add(patienten_node)
            patient_jahr(patienten_node, rechnung_list, bre_list, la_list)
Next