void OnSelectedIndexChanged (object sender, EventArgs e)
{
TabPage page = ((TabControl) sender).SelectedTab;
if (page == _tabPage2) {
_control = new TestControl ();
_control.Dock = DockStyle.Fill;
_tabPage2.Controls.Clear ();
_tabPage2.Controls.Add (_control);
} else {
if (_control != null)
_control.Dispose ();
_control = null;
}
}