gridview and checkbox

foreach(GridViewRow row in gv1.Rows)
        {
//Give your cell index where checkbox resides e.g 0 and if checkbox is only a control in a cell then just give 0 as a index in control otherwise change it accordingly            
if(((CheckBox)row.Cells[0].Controls[0]).Checked)
            {
// Apply your operation here on checked checkbox row.
            }
        }