private void Start_btn_Click(object sender, RoutedEventArgs e)
{
mqttconnection = new MqttConnection(this);
mqttconnection.Host = URL_Box.Text;
mqttconnection.Port = Convert.ToInt32(Port_Box.Text);
mqttconnection.Topic = TopicBox.Text;
mqttconnection.MessageText = MessageBox.Text;
mqttconnection.Intervaltime = (float)IntervalNr.Value;
mqttconnection.Device_Nr = Convert.ToUInt32(DeviceNr.Value);
StartSpinner.Visibility = Visibility.Visible;
Start_btn.IsEnabled = false;
Stop_btn.IsEnabled = true;
Label_error.Content = "";
Label_Status.Content = "Connecting ";
mqttconnection.MQTTConnection_start();
}