Hi dreamyfriend,
Your c# program may have 2 buttons.
1. ON
2. OFF
When you click on ON, it will send this information through a serial port to the microcontroller's RX port. The microcontroller will turn ON a triac, this triac will turn ON/OFF the electric bulb.
Or to avoid microcontroller I may use the cd/dvd drive. C# ON button will eject the drive and the tray will hit a microswitch, which would turn ON the bulb. To turn it OFF, I can then download "Eject and Close CD Tray Version 1.0.0.0" a commandline application from Softpedia to open and close cd/dvd drive. Then call this program from C# GUI which contains 2 buttons as mentioned before
1. ON
2. OFF
Ok, hope others may give you better suggestion.
Best regards.