public void Clear()
{
showSpeaker = null;
nameLabel.Text = "";
titleLabel.Text = "";
companyLabel.Text = "";
bioTextView.Text = "";
image.Image = null;
LayoutSubviews (); // show the grey 'no speaker' message
}
// for masterdetail
public void Update(SpeakerDetailsViewModel viewModel)
{
showSpeaker = viewModel;
Update ();
LayoutSubviews ();
}