public ActionResult GridData(int start = 0, int itemsPerPage = 20, string orderBy = "ID", bool desc = false)
{
Response.AppendHeader("X-Total-Row-Count", db.Activities.Count(a => a.Event.ID == eventID).ToString());
ObjectQuery<Activity> activities = (db as IObjectContextAdapter).ObjectContext.CreateObjectSet<Activity>();
activities = activities.OrderBy("it." + orderBy + (desc ? " desc" : ""));
return PartialView(activities.Where(a => a.Event.ID == eventID).Skip(start).Take(itemsPerPage));
}