string str = Server.MapPath(".");
            string fileName =str+ @"\data\dataXml.xml";
            XDocument doc = XDocument.Load(fileName);
            IEnumerable<XElement> missions = doc.Root.Elements("mission");

          //  XElement mo = tracks.ElementAt(0);
            DropDownList1.DataSource = missions.ToList();
            DropDownList1.DataTextField = "missionName";
            DropDownList1.DataBind();

<mission id="1" missionName="SIMON1">
 <image link="assets/missionImaga01.jpg" type="iner" />
    <image link="assets/missionImaga02.jpg" type="content" />
</mission>...