Before we publish the data, we need to consider what data is relevant to publish. We want to avoid spamming the broker, or any subscribers. We define relevant to mean values that show a significant change (more than one percentage point), or values after significant silence (at least 15 seconds):

private void PublishLight(double Light) 
{ 
   DateTime Now = DateTime.Now; 
 
   this.lastLight = Light; 
 
   if ((!this.lastPublishedLight.HasValue || 
         Math.Abs(this.lastPublishedLight.Value-Light) >= 1.0 || 
         (Now-this.lastLightPublishTime).TotalSeconds >= 15.0) && 
         this.mqttClient != null && 
         this.mqttClient.State == MqttState.Connected) 
   { 
         this.lastPublishedLight = Light; 
         this.lastLightPublishTime = Now; 

We then proceed by creating the string we want to publish. Our goal is to publish this string on the Waher/MIOT/[DEVICE_ID]/Light topic, where [DEVICE_ID] is replaced by the real device ID:

         string ValueStr = ToString(Light, 2) + " %";