private void PrinterLoggerCallback(string message, string printer_serial) { if (printer_serial == "Detecting") { message = "Detecting>" + message; printer_serial = "00-00-00-00-00-000-000"; } var spoolerMessage = new SpoolerMessage(MessageType.LoggingMessage, new PrinterSerialNumber(printer_serial), Base64Convert.Base64Encode(message)); lock (logging_queue) { logging_queue.Add(spoolerMessage); } }