public int IndexOfUniqueSessionId(WTSUniqueSessionId _UniqueSessionId)
 {
     for (int i = 0; i < this.Count; i++)
     {
         if (this[i].UniqueSessionId == _UniqueSessionId)
         {
             return(i);
         }
     }
     return(-1); // non found
 }
        //public override event NotifyCollectionChangedEventHandler CollectionChanged;
        //protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        //{
        //    var eh = CollectionChanged;
        //    if (eh != null)
        //    {

        //        Dispatcher dispatcher = (from NotifyCollectionChangedEventHandler nh in eh.GetInvocationList()
        //                                 let dpo = nh.Target as DispatcherObject
        //                                 where dpo != null
        //                                 select dpo.Dispatcher).FirstOrDefault();

        //        if (dispatcher != null && dispatcher.CheckAccess() == false)
        //        {
        //            dispatcher.Invoke(DispatcherPriority.DataBind, (Action)(() => OnCollectionChanged(e)));
        //        }
        //        else
        //        {
        //            foreach (NotifyCollectionChangedEventHandler nh in eh.GetInvocationList())
        //                nh.Invoke(this, e);
        //        }
        //    }
        //}

        public WTSSession this[WTSUniqueSessionId _UniqueSessionId]
        {
            get
            {
                foreach (WTSSession s in this)
                {
                    if (s.UniqueSessionId == _UniqueSessionId)
                    {
                        return(s);
                    }
                }
                return(null);
            }
        }