You can use a timer to force the page redirect to login page after 20 minutes.
<body>
<form id="form1" runat="server">
<asp:scriptmanager id="ScriptManager1" runat="server" xmlns:asp="#unknown">
</asp:scriptmanager>
<asp:timer id="Timer1" runat="server" interval="1200000" ontick="Timer1_Tick" xmlns:asp="#unknown">
</asp:timer>
</form>
</body>
Code behind:
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Timer1_Tick(object sender, EventArgs e)
{
Response.Redirect("~/ContentPages/Common/Home.aspx", true);
}
}