As has been mentioned already C# is not the best thing to use for a cheap project as you requested.

Could I suggest the PIC Microcontroller from Microchip. You can get free (Lite) C compilers. You'll pick up C quickly if you know C#. Microchip do little demo boards which have a microcontroller and prototype area on them. Maybe something like a PicKit will do.

Again, I know its not a C# suggestion.

I use these devices for little projects myself. Almost everything on one chip. Useful little chips.

Andy