in some way these codes will help you very much if you need
to know file extension.
method below returns true if extension are any of the following -

beginners of .net programming can't guess sometime that
how easy is sending mail through .net.there are many ways
to do that.but i am writing here the easiest method to send
mail in c# with .net.It doesn't involve a lot's of coding.
all is built in and no more components.

Nowadays internet is being part of our life.So you need to
be cautious when you browsing internet.Following are some
guidelines to be safe -

HttpCookie is a very good way to store small amount of data
in asp.net application/website.you can access cookie value in
any page once set in a page.cookie can stay for long time in the
user's computer.