for (int i = 0; i < 5; i++) { TabPanel tab = new TabPanel(); tab.Controls.Add(new UCPrevTabTH() { ID = "tab" + i.ToString() }); PlaceHolder ph new PlaceHolder() { ID "ph" + i.ToString() }; UCPrevTabTH uc = new UCPrevTabTH(); uc = (UCPrevTabTH)LoadControl("UCPrevTabTH.ascx"); uc.ID = "uc" + i.ToString(); ph.Controls.Add(uc); tab.Controls.Add(ph); tabs.Tabs.Add(tab); }