In Login page: create a session to store user id
ex:
Session["userName"] = userName;
check in every page that the session value is exist or time out.
ex:
if (Session["userName"] != null)
{
}
else
{
Response.Redirect("Login.aspx", false);
}
when you click in logout button then redirect in logout.aspx page
in Logout.aspx page remove your all session:
Session.Abandon();
Session.Clear();
Session.RemoveAll();
System.Web.Security.FormsAuthentication.SignOut();
Response.Redirect("Login.aspx", false);
please, adjust your code according to this sample code.
Thank you.
Rashed:: Bangladesh.