private void CheckGroupBoxElementsCheckChanged(object sender, ItemCheckEventArgs e)
{
if (SuppressEvents) return;
var id = e.Index + 1;
if (e.NewValue == CheckState.Checked && !this._state.guard_element_set.Contains(id))
this._state.guard_element_set.Add(id);
else if (e.NewValue == CheckState.Unchecked && this._state.guard_element_set.Contains(id))
this._state.guard_element_set.Remove(id);
}