The C# program (needs cleaning)
/// Startup code ///
IPHostEntry host;
string localIP = "0";
host = Dns.GetHostEntry(Dns.GetHostName());
foreach (IPAddress ip in host.AddressList)
{
  if (ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
  {
    localIP = ip.ToString();
    localIP = localIP.Substring(localIP.LastIndexOf(".") + 1);
  }
}

//20171224
Program.Setup(()=>{
  Program.UseWidget("vip/control/sonoff");
});

Program
  .AddOption("ClientId", "Sonoff" + localIP, "0. Enter unique ID for this client", "text")
  .
AddOption("ServerAddress", "192.168.11.210", "1. MQTT server address", "text")
  .
AddOption("ServerPort", "1883", "2. MQTT server port", "text")
  .
AddOption("ServerTopicStatus", "stat/sonoff2/POWER", "3. Topic", "text")
  .
AddOption("ServerTopicCmd", "cmnd/sonoff2/power", "4. Topic", "text")
  .
AddFeature("", "Switch", "HomeGenie.SwitchHeater", "Enable Smart Light Control", "checkbox")
  .
AddFeature("", "", "MQTT", "Publish module on MQTT network", "checkbox")
  .
Run();

//// Program ////
/*
Status 
stat/sonoff2/POWER ON
stat/sonoff2/POWER OFF

cms
cmnd/sonoff2/power ON
cmnd/sonoff2/power OFF
*/
string server = Program.Option("ServerAddress").Value.Trim();
int port = 1883; 
int.TryParse(Program.Option("ServerPort").Value, out port);
string topicStatus = Program.Option("ServerTopicStatus").Value.Trim();
string topicCmd = Program.Option("ServerTopicCmd").Value.Trim();
string clientid = Program.Option("ClientId").Value.Trim();
string username = Program.Option("Username").Value.Trim();
string password = Program.Option("Password").Value.Trim();

string local_TopicIn = "stat/sonoff2/POWER" ;//"stat/"+topic+"/";topicStatus ; //
string local_TopicOut = "cmnd/sonoff2/power";
string local_Switch = "Control.SOnOff"; 
string local_Switch_off = "Control.Off"; 
string remote_Switch_on = "ON" ;
string remote_Switch_off = "OFF" ;

int delayCnt = 0;

// This program will be displayed as a simple button
//Program.UseWidget("vip/control/sonoff");

var LastTime = DateTime.Now ;
var MqttIsConnected = false;
var ProgName = "MQTT SonOff";
Program.Notify(ProgName, "starting");
Pause(1);

if (server == "")
{
  Program.Notify( ProgName, "Please configure server address");
  Pause(5);
  return;
}
else
{
  Program.Notify( ProgName, "Connecting to " + server + "...");
  try
  {
    if (username != "")
    {
      MqttClient.WithCredentials(username, password);
    }
    
    MqttClient.Service(server).Connect(port, clientid);
    Program.Notify( ProgName, "Connected! "+local_TopicIn);
    MqttIsConnected = true;
  }
  catch (Exception e)
  {
    Program.Notify( ProgName, e.Message);

    Pause(5);
    return;
  }
}

// start lezen
MqttClient.Subscribe(local_TopicIn, (mtopic, mpayload) => {
  Program.Notify(local_TopicIn + "==" , mpayload );
  var parts = mtopic.Split('/'); // check of json is
  if (parts.Length >1) // hebben we een bericht -->2
  {
    try
    {
      if (mpayload == "ON")
      {   
        Program.RaiseEvent( "Status.Level", "100",mpayload); //sensorstatus      
      }
      
      if (mpayload == "OFF")
      { Program.RaiseEvent("Status.Level", "0",mpayload); //sensorstatus        
      }
       
    }catch (Exception e) {
      Program.Notify( ProgName+" ERROR!", e.Message);

    }
    
    Pause(2);
  }
});


When.WebServiceCallReceived("HomeAutomation.HomeGenie.Automation", (args) => {
    // All API requests going to the "MyProgram.Domain"
    // will hit this piece of code.
    // e.g. for the "On" command, <args> will contain the string
    // "MyProgram.Domain/1/Control.On", so...
    string[] req = ((string)args).Split('/');
    string domain = req[0], address = req[1], command = req[2];
    // be optimistic
    var response = "{ \"ResponseValue\" : \"Ok\" }";
    // get a reference to the addressed module
    var module = Modules.InDomain(domain).WithAddress(address).Get();
    // process the command
	Program.Notify(command," Button pressed " + address + " dom. "+domain );
      Pause(2);
    switch (command)
    {
        case "Control.On":
            // set the status of the module to on
      		MqttClient.Publish("cmnd/sonoff2/power","ON");
            //Program.RaiseEvent(module, "Status.Level", "1", "Switched on");
      		//MqttClient.Publish(local_TopicOut,remote_Switch_on);
      		
            break;
        case "Control.Off":
            // set the status of the module to off
     		 MqttClient.Publish("cmnd/sonoff2/power","OFF");
            //Program.RaiseEvent(module, "Status.Level", "0", "Switched off");
      		//MqttClient.Publish(local_TopicOut,remote_Switch_off);
      		
            break;
        default:
            response = "{ \"ResponseValue\" : \"Error\" }";
            Program.Notify("MyProgram", "Unrecognized command received");
            break;
    }

    return response;
});
while (Program.IsRunning && MqttIsConnected) 
{Pause(3);}

//Program.GoBackground();