async void OnDeviceCloseClicked(object sender, EventArgs e)
{
await _printSemaphore.WaitAsync();
if (_printer != null)
{
// If there's nothing to do with the printer, call "closeService" method to disconnect the communication between Host and Printer.
await _printer.closeService();
_printer = null;
btnPrintText.IsEnabled = false;
btnCloseService.IsEnabled = false;
btnOpenService.IsEnabled = true;
}
_printSemaphore.Release();
}
