how to send email with attactment using C#

Question

hallo

how to send email with attachtment using c#  ?
there are several example in internet about it ,but have' nt found one working
I have followed the instruction,including setting control panel----> administrative tools--->
IIs--->default SMTP Virtual Server --->properties--->Access--->Relay---> add 127.0.0.1 --->

--->delivery--->fill smart host with localhost ,change smart host with "mail.yahoo.com"

all doesnt work.

any help  ?

thank you

han