private void login_Click(object sender, RoutedEventArgs e)
        {
            string usr = username.Text;
            string psw = password.Text;

            if (psw != string.Empty && usr != string.Empty)
            {
                UserContext usc = ServiceCalls.Login(usr, psw);

                if (usc.Authenticated)
                {
                    Frame.Navigate(typeof(Main), new NavigationContext()
                    {
                        UserContext = usc
                    });
                }
                else
                {
                    status.Text = "Failed to login.";
                }
            }
        }