private async void button_Clicked(object sender, EventArgs e)
{
    await MercatorTunnel.PlatformMaui.Api.ScanBarCode(MercatorApi.Api.ApiLangue, this, Navigation, button4, Colors.White, ThemeColor, delegateSetResult: BarcodeScanned);
}

private void BarcodeScanned(string barcode)
{
    if (barcode == null) // on a annulé
        _ = MercatorPenguin.Dialogs.Stop(this, "Geen barcode gelezen!");
    else
        _ = MercatorPenguin.Dialogs.Stop(this, $"Barcode gelezen = {barcode}!");
}