in databound event
foreach(dataview/datagrid items)
{
find the linkbutton(objLinkButton) row.findcontrl
("LinkButtonID")
objLinkButton.attributes.add("onClick","return "validates
();")
}

Make object of particular button 

Ex:

LinkButton lnbDelete=(LinkButton) e.Item.FindControl
("Delete");

After that we can use it with JavaScript:
lnbDelete.Attributes.Add("Onclick","javascript:return 
confirm('Are you sure you want to delete this?');");