Login or Logout process with the help of session

First check session is create or not
if (Session["email"] == null)
        {
            LinkButton2.Text = "Login";
        }
        else
        {
            LinkButton2.Text = "Logout";
            Label1.Text = "Welcome "+Session["email"].ToString();
        }

 Now delete all session if create(at the time of click on Logout button)
if (Session["email"] == null)         
        {
            Response.Redirect("login.aspx");
        }
        else
        {
            HttpContext.Current.Session["username"] = null;        //desable session
            HttpContext.Current.Session["password"] = null;
            HttpContext.Current.Session.Abandon();
            Response.Redirect("home.aspx");
        }