//Login.aspx
private Rti.Admin.Login lg = new Rti.Admin.Login();
    protected void Page_Load(object sender, EventArgs e)
    {
        IsLogged();
    }

    protected void btnLogin_Click(object sender, EventArgs e)
    {
        lg.LoginCheck(tboxId.Text, tboxPwd.Text);
        IsLogged();
    }
    private void IsLogged() {
        if (lg.IsLogged())
        {
            if (Session["User"] == null)
            {
                Session["User"] = lg.Uid;
            }
            Response.Redirect("manager.aspx");
        }
    }
//Manage.aspx

private Rti.Admin.Login lg = new Rti.Admin.Login();
    private SqlConnection cn = new SqlConnection(ConfigurationManager.ConnectionStrings["Act2008"].ConnectionString);
    private SqlCommand cmd = new SqlCommand();
    protected void Page_Load(object sender, EventArgs e)
    {
        IsNotLogged();

    }
    private void IsNotLogged()
    {
        if (!lg.IsLogged())
        {
            Response.Redirect("index.aspx");
        }
    }