public override void Add(Control value) { if (value is TabPage == false) { throw new ArgumentException("value is not TabPage"); } var tabPage = value as TabPage; tabPage.Anchor = AnchorStyles.Left | AnchorStyles.Top | AnchorStyles.Right | AnchorStyles.Bottom; tabPage.Bounds = owner.DisplayRectangle; tabPage.Visible = false; base.Add(value); owner.AddTabPage(tabPage); }