how to fetch a particular column value within the gridview when grid is binded with a db table?

Hi,

how to fetch a particular column value within the gridview, when it is binded with a db table on page_load event and when to fetch the value in button click event

for ex: gridview binded with emp table on page load event and need to get the emp id on button click event without using any extra web control within the template field of gridview.

Regards,
Rajendra