Insertar registro al inicio archivo txt

Public i As Integer = 0
Private Sub btnaceptar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnaceptar.Click
        Dim filename As String = Directory.GetCurrentDirectory & "\log.txt"
        Dim tempfile As String = Path.GetTempFileName()
        i += 1
        Using writer = New StreamWriter(tempfile)
            Using reader = New StreamReader(filename)
                writer.WriteLine(Now.ToString("dd-MM-yyyy HH:mm:ss:ffff") & "|" & tbinsertar.Text.Trim & "|" & i)
                While Not reader.EndOfStream
                    writer.WriteLine(reader.ReadLine())
                End While
            End Using
        End Using
        File.Copy(tempfile, filename, True)
        File.Delete(tempfile)
    End Sub

fuente: https://stackoverflow.com/questions/2401523/how-to-insert-row-in-first-line-of-text-file