Private Sub cob_TextEditor_Schriftgrösse_SelectedIndexChanged(sender As _
      Object, e As EventArgs) Handles _
      sym_TextEditor_cob_Schriftgrösse.SelectedIndexChanged
            If LCase(IO.Path.GetExtension(dateiname)) = ".txt" Then
                ' Bei Text-Datei ganzen Text umformatieren
                tsc_TextEditor_RTFBox.Font = New Font( _
                  sym_TextEditor_cob_Schriftart.Text, _
                  sym_TextEditor_cob_Schriftgrösse.Text)
                My.Settings.SchriftTextEditorFont = New Font( _
                sym_TextEditor_cob_Schriftart.Text, CInt( _
                sym_TextEditor_cob_Schriftgrösse.Text))
            Else
                ' Bei RTF-Datei nur selektierten Text umformatieren
                If tsc_TextEditor_RTFBox.SelectionFont IsNot Nothing Then
                    ' alle Zeichen identisch formatiert
                    tsc_TextEditor_RTFBox.SelectionFont = New Font( _
                      tsc_TextEditor_RTFBox.SelectionFont.FontFamily, CInt( _
                      sym_TextEditor_cob_Schriftgrösse.SelectedItem), _
                      tsc_TextEditor_RTFBox.SelectionFont.Style)
                Else
                    ' Selektion mit unterschiedlicher Formatierung
                    ' ???
                End If
            End If
        end sub

  'Schriftgröße ändern bei unterschiedlichen Fonts:
  Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) _
    Handles ComboBox1.SelectedIndexChanged
    Dim fg = CInt(ComboBox1.SelectedItem) 'Auflistung von Zahlen
    Dim rtb = RichTextBox1
    If rtb.SelectionLength > 0 Then
      Dim rt = rtb.SelectedRtf
      For Each m As Match In Regex.Matches(rt, "\\fs\d{1,3}", _
        RegexOptions.RightToLeft)
        rt = rt.Remove(m.Index, m.Length).Insert(m.Index, $"\fs{fg * 2}")
      Next
      rtb.SelectedRtf = rt
    End If
  End Sub

        Dim vara As Integer
        Dim beginHeader As Long = plaintext.IndexOf("{\fonttbl{")
        Dim endHeader As Long = plaintext.IndexOf("}}")
        Dim einträge = plaintext.Substring(beginHeader + 9, endHeader - _
          beginHeader - 9).Split("}")
        fontlisteRTFDokument.Clear()
        For vara = 0 To einträge.Length - 1
            Dim beginFont As Long = einträge(vara).IndexOf(" ")
            Dim endFont As Long = einträge(vara).IndexOf(";")
            fontlisteRTFDokument.Rows.Add(einträge(vara).Substring(beginFont + _
              1, endFont - beginFont - 1))
            ' Test der Tabellenübernahme: Debug.Print(einträge(vara).Substring( 
            ' beginFont + 1, endFont - beginFont - 1))
        Next

    Private Sub ändereSelectedSchriftschnitt(sSchnitt As Integer)
 
        Dim rtb = tsc_TextEditor_RTFBox
 
        ' Selektion merken
        Dim rtbs = rtb.SelectionStart
        Dim rtbsl = rtb.SelectionLength
 
        If rtb.SelectionLength > 0 Then
 
            Dim rt = rtb.SelectedRtf
 
            ' Bold Start und Ende entfernen
            If (sSchnitt And 1) = 1 Or (sSchnitt And 1) = 0 Then
                For Each m As Match In Regex.Matches(rt, "\\b0", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\b\s", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\b", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length) 
                Next
            End If
 
            ' Italic Start und Ende entfernen
            If (sSchnitt And 2) = 2 Or (sSchnitt And 1) = 0 Then
                For Each m As Match In Regex.Matches(rt, "\\i0", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\i\s", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\i", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length) 
                Next
            End If
 
            ' Underline Start und Ende entfernen
            If (sSchnitt And 4) = 4 Or (sSchnitt And 1) = 0 Then
                For Each m As Match In Regex.Matches(rt, "\\ulnone", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\ul\s", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\ul", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
            End If
 
            ' Strikeout Start und Ende entfernen
            If (sSchnitt And 8) = 8 Or (sSchnitt And 1) = 0 Then
                For Each m As Match In Regex.Matches(rt, "\\strike0", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\strike\s", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length)
                Next
                For Each m As Match In Regex.Matches(rt, "\\strike", _
                  RegexOptions.RightToLeft)
                    rt = rt.Remove(m.Index, m.Length) 
                Next
            End If
 
            ' Schriftschnitt am Anfang und Ende der Selektion setzen
            Dim n As Match
            n = Regex.Match(rt, "\\pard")
 
            ' Bold
            If (sSchnitt And 1) = 1 Then
                rt = rt.Insert(n.Index, $"\b") & rt & "\b0"
            End If
 
            ' Italic
            If (sSchnitt And 2) = 2 Then
                rt = rt.Insert(n.Index, $"\i") & rt & "\i0"
            End If
 
            ' Underline
            If (sSchnitt And 4) = 4 Then
                rt = rt.Insert(n.Index, $"\ul") & rt & "\ulnone"
            End If
 
            ' StrikeOut
            If (sSchnitt And 8) = 8 Then
                rt = rt.Insert(n.Index, $"\strike") & rt & "\strike0"
            End If
 
            ' In RTF übernehmen
            rtb.SelectedRtf = rt
 
            ' Selektion erneuern
            rtb.SelectionStart = rtbs
            rtb.SelectionLength = rtbsl
        End If
    End Sub