This way
HTML
<%@ Register TagPrefix="cc1" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<cc1:ToolkitScriptManager runat="server"></cc1:ToolkitScriptManager>
<cc1:TabContainer runat="server" ID="TabContainer1">
<cc1:TabPanel runat="server" ID="TabPanel1">
<HeaderTemplate>
TabPanel 1
</HeaderTemplate>
<ContentTemplate>
ContentTemplate of TabPanel 1
</ContentTemplate>
</cc1:TabPanel>
</cc1:TabContainer>
</div>
</form>
</body>
</html>
C#
protected void Page_Load(object sender, EventArgs e)
{
TabPanel tbPanel = new TabPanel();
tbPanel.HeaderText = "TabPanel 2";
this.TabContainer1.Controls.Add(tbPanel);
}
