private void btnGestionarVentas_Click(object sender, RoutedEventArgs e)
        {
            GestionarVentas gv = new GestionarVentas(nomUsuario);

            gv.Show();
            this.Close();
        }
        private void btnVolver_Click(object sender, RoutedEventArgs e)
        {
            GestionarVentas gv = new GestionarVentas();

            gv.Show();
            this.Close();
        }