public class MySensor
{
   public delegate void MySensorFiredHendler(object fired_value);
   public event MySensorFiredHendler MySensorFired;

   Sensor _sensor
   public MySensor ()
   {
       _sensor = new Sensor();
       _sensor.SensorChangeValue += _sensor_SensorChangeValue;
   }

   void _sensor_SensorChangeValue(Sensor sender, SensorChangeValueEventArgs args)
   {
       object FiredValue = args.Value;
       if (MySensorFired!= null)
                MySensorFired(FiredValue);     
   }
}

private void button1_Click(object sender, EventArgs e)
 {
            MySensor s = new MySensor();
            s.MySensorFired += s_MySensorFired;
 }

void s_MySensorFired(object fired_value)
{
   this.text = fired_value.ToString();
}

void s_MySensorFired(object fired_value)
{
   this.BeginInvoke((Action)(() =>
   {
       this.text = fired_value.ToString();
    }));
}

this.BeginInvoke((Action)(() => ...

this.text = fired_value.ToString();