Disbale DataGridViewRow unselect when CTRL is pressed

If the CTRL key is pressed and you click a selected DataGridViewRow the row is unselected. How can I stop this?

From stackoverflow

• That is the standard behaviour for multi-selection using [Ctrl]. Why would you break the user's expected interface? You could possibly hack around it by detecting selection changes (I'll look...)

  (edit) - yes, seems to work if you hook SelectionChanged, something like:

  DataGridViewRow[] lastSelectedRows = new DataGridViewRow[0];
  void grid_SelectionChanged(object sender, System.EventArgs e) {
      if ((Control.ModifierKeys & Keys.Control) == Keys.Control) {
          foreach (DataGridViewRow row in lastSelectedRows) {
              if (!row.Selected) row.Selected = true;
          }            
      }
      DataGridViewSelectedRowCollection selected = grid.SelectedRows;
      lastSelectedRows = new DataGridViewRow[selected.Count];
      selected.CopyTo(lastSelectedRows, 0);
  }
  

• How would you unselect something if it is accidentally selected?