Learn a little bit about your printer command language i.e. the famous ESC/POS (get ref manual from EPSON website)
Then send those commands directly to the printer by using this code http://support.microsoft.com/kb/322090/en-us
I suppose it is a desktop app what you are coding there. If it were an ASP.NET website, then things change a bit. Just let me know if this last one is your case.