Steganography hide text in image

Dim PicBytes As Long = PicFileStream.Length
        Dim PicExt As String = PicBuffer.Extension
        Dim PicByteArray(PicBytes) As Byte
        PicFileStream.Read(PicByteArray, 0, PicBytes)
        Dim SentinelString() As Byte = {73, 116, 83, 116, 97, 114, 116, 115, 72, 101, 114, 101}

        Dim PlainText As String = txtchin
        Dim PlainTextByteArray(PlainText.Length) As Byte
        For i As Integer = 0 To (PlainText.Length - 1)
            PlainTextByteArray(i) = CByte(Asc(PlainText.Chars(i)))
            Application.DoEvents()
        Next