private void OnClearAll()
 {
     var tickersCopy = new TickerFileViewModel[tickers.Count];
     tickers.CopyTo(tickersCopy, 0);
     tickers.Clear();
     foreach (var t in tickersCopy.Where(x => x.LoadState == AsyncState.Running))
         t.RemoveNotification(OnLoadingEnd);
     LoadingCount = 0;
     ErrorCount = 0;
     LoadedCount = 0;
 }