Public Function FileLineCount(ByVal Filename As String) As Integer
        Dim Lines As Integer = 0
 
        Using oStream As New IO.FileStream(Filename, IO.FileMode.Open, _
          IO.FileAccess.Read)
            ' Blockgröße
            Dim BlockSize As Integer = 16384
 
            Dim Bytes(BlockSize) As Byte
            Dim ReadSize As Integer
            Dim StartIndex As Integer
 
            ' Datei blockweise auslesen, bis Dateiende erreicht
            Do
                ReadSize = oStream.Read(Bytes, 0, BlockSize)
 
                ' Anzahl Zeilenumbruchzeichen ermitteln
                StartIndex = -1
                Do
                    StartIndex = Array.IndexOf(Bytes, CByte(13), StartIndex + _
                      1, ReadSize - StartIndex)
                    If StartIndex >= 0 Then Lines += 1
                Loop Until StartIndex < 0
 
            Loop Until ReadSize = 0
            oStream.Close()
        End Using
 
        Return Lines
    End Function