public void Insert(int index, Widget widget)
{
if (m_widgets.Contains(widget))
{
throw new InvalidOperationException("Child widget already present in container.");
}
if (index < 0 || index > m_widgets.Count)
{
throw new InvalidOperationException("Widget index out of range.");
}
widget.ChangeParent(m_containerWidget);
m_widgets.Insert(index, widget);
m_containerWidget.WidgetAdded(widget);
m_version++;
}
