byte[] fd;

OpenFileDialog o = new OpenFileDialog();

if (o.ShowDialog() != DialogResult.Cancel)

{

    filename = o.FileName;

    FileStream st = new FileStream(filename, FileMode.Open, FileAccess.Read);

    FileInfo fi = new FileInfo(filename);

    fd = new byte[fi.Length];

    st.Read(fd, 0, (int)fi.Length);

    st.Close();

}