user login logout

 protected void LoginButton_Click(object sender, EventArgs e)
    {
        username = Guid.NewGuid().ToString();
        Response.Write(username);
        FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(username, true, 20);
        string cookiestr = FormsAuthentication.Encrypt(ticket);
        HttpCookie ck = new HttpCookie(FormsAuthentication.FormsCookieName, cookiestr);
        if (true)
        {
            ck.Path = FormsAuthentication.FormsCookiePath;
        }
        Response.Cookies.Add(ck);
        FormsAuthentication.RedirectFromLoginPage(username, false);
    }
    protected void LogoutButton_Click(object sender, EventArgs e)
    {
        FormsAuthentication.SignOut();
        Response.Redirect("Default.aspx");
    }