private void update_preview_text() {
bool no_matches = prev_search_.text == "" || (prev_search_.use_regex && prev_search_.regex == null);
preview.Text = "Previewing surrounding " + preview_items_.Count + " rows. ";
if (no_matches) {
preview.Text += " NO MATCHES.";
return;
}
preview.Text += "" + matches_.Count + " matches";
if (matches_.Count > MAX_SHOW_ROWS)
preview.Text += ", showing only " + result.GetItemCount();
}