You cannot call server-side code
‘directly’ from client-side code. That
is because by design, the server side
code executes at server side and
client side code at the client.
However there are some workarounds. To
call serverside code from javascript,
you will need to use AJAX, and the
easiest way out, is to use the ASP.NET
AJAX Extensions.
Check this link
How to call Server Side function from Client Side Code using PageMethods in ASP.NET AJAX
