''' <summary>Ermittlung einer bestimmten Zeile in einer Text-Datei</summary>
 ''' <param name="filepath">voller Pfad der zu lesenden Datei</param>
 ''' <param name="linenumber">Index der zu lesenden Zeile (eins-basiert)</param>
 ''' <param name="IgnoreEmptyLines">Leere Zeilen bei Indizierung ignorieren?</param>
 ''' <param name="Message">Fehlermeldung oder Leere Rückgabe</param>
 ''' <returns>gelesene Zeile oder Nothing</returns>
 Private Function ReadLine(ByVal filepath As String, _
                           ByVal linenumber As Integer, _
                          Optional ByVal IgnoreEmptyLines As Boolean = True, _
                          Optional ByRef Message As String = "") As String
 
        If Not IO.File.Exists(filepath) Then
            Message = "Datei nicht gefunden" : Return Nothing
        End If
        If New IO.FileInfo(filepath).Length = 0 Then
            Message = "Leere Datei" : Return Nothing
        End If
        If linenumber < 1 Then
            Message = "Ungültiger Parameter: LineNumber" 
            Return Nothing
        End If
 
        Dim ln As Integer = 0
        Dim enc As System.Text.Encoding = System.Text.Encoding.UTF8
        Dim line As String, ret As String = Nothing
        Try
            Using sr As New IO.StreamReader(filepath, enc, False)
                Do
                    line = sr.ReadLine()
                    If Not IgnoreEmptyLines OrElse _
                       Not line = String.Empty Then
                        ln += 1
                        If ln = linenumber Then ret = line
                    End If
                Loop Until ln = linenumber Or sr.EndOfStream
            End Using
            If ret Is Nothing Then
                Message = "Ungültiger Parameter: LineNumber"
            Else
                Message = ""
            End If
            Return ret
        Catch ex As Exception
            Message = ex.Message : Return Nothing
        End Try
    End Function

  Dim message As String = ""
  Dim line As String = _
       ReadLine("C:\daten\aaa.txt", 1, False, message)
  If line Is Nothing Then
     MsgBox(message)
  Else
     MsgBox(line)
  End If