สอบถามเรื่องการเช็คบรรทัดสุดท้ายครับ จาก File .txt ลง DataGridView

Dim streamReader As IO.StreamReader = New IO.StreamReader(showcell)
        'Dim lastLine As String = lines.Item(lines.Count - 1)
        Try
            While streamReader.Peek() <> -1
                rowvalue = streamReader.ReadLine()
                sb = rowvalue.Substring(1, 7)
                count = Len(sb)
                DataGridView1.Rows.Add(New String() {sb})
                ' txtOrDate.Text = lastLine
            End While
        Catch ex As Exception
            Me.txtOrDate.Text = "Read failed. (" & ex.Message & ")"
        End Try