BoundField tfMail = new BoundField();
        tfMail.DataField = "IndirizzoEmail";
        tfMail.ShowHeader = true;
        tfMail.DataFormatString = "<a href=javascript:void(window.open('PopUp.aspx?Matricola={0}',null,'width=400,height=150'))>
        <img src=\"images/ico_mail.png\" border='0'/></a>";
        gv.Columns.Add(tfMail);