WPF

namespace SampleGUIs
{
    public partial class MainPage : UserControl
    {
        private ChildWindow cw;

        public MainPage()
        {
            InitializeComponent();
            cw = new ChildWindow();
            cw.Closed += new EventHandler(ShowMessage); //now this methos is not shown in intellisense
        }
    }
}

namespace SilverlightApplication9
{
    public partial class PopupWindow : ChildWindow
    {
        public PopupWindow()
        {
            InitializeComponent();
            this.Title = "Child Window"; //not shown in intellisense so not available
        }
    }
}