Problem With Gridview /Datalist

Question

i have gridview in which i hv taken template field in template field i hv added image button on which i hv displayed the image stored in the database. but now i facing the problem  that when i tried to open the link attached with the image button it opens the link of first image not to the other links. Although each image has its image_id which is primary key and i want to open the link according to image_id. but my problem is how to find the image_id of each individual image.
so that i can open the respective file that i want.