Website Devlopment: Authorization and Session Issues

Hello, I am developing a Website using VS 2012, my webapp project has Defualt.aspx , which is a login page and the project has many others .aspx pages. My intention is to restrict non-logged in users from accessing any  page other than Default.aspx, and also  may be redirect the user to Default.aspx. I also want to redirect user to Default.aspx when the session gets expired. I can accomplish both these by Checking for SessionID in Page_load of all pages other than Default.aspx, something like below: if (Session["UserID"] == null) {      Response.Redirect("~/Default.aspx"); } Can someone advise if this will be a good approach to follow? I am wondering if there is a way to do this by authorization setting in web.config, though I tried and it didn't work for me. TIA!