Есть запрос  

 var userprofile = from n in db.Users
                where n.UserLogin == name
                select new { n.UserMail, n.UserFIO ......... Х };

object F (string selfield)
{
var userprofile = from n in db.Users
                where n.UserLogin == name
                select new { selfield}

return userprofile.First().selfield;
}

object getval(object r, string n)
        {
            
            System.Reflection.PropertyInfo prop = r.GetType().GetProperty(n);
            if (prop != null)
                return prop.GetValue(r, null);
            return n;

        }


...
                var userprofile = from n in db.Users
                                  where n.UserLogin == name
                                  //select new { n };
                                  select  getval(n, propertyName);
...