The relay is connected to our digital output pin 9 on the Arduino board. As such, controlling it is a simple call to the digitalWrite() method on our arduino object. Since we will need to perform this control action from various locations in code in later chapters, we'll create a method for it:

internal async Task SetOutput(bool On, string Actor) 
{ 
   if (this.arduino != null) 
   { 
         this.arduino.digitalWrite(9, 
               On ? PinState.HIGH : PinState.LOW); 

The first parameter simply states the new value of the control parameter. We'll add a second parameter that describes who is making the requested change. This will come in handy later, when we allow online users to change control parameters.