private void OnTickerSymbolChanged(PropertyChangedEventArgs eventArgs) { var args = eventArgs as PropertyValueChangedEventArgs <string>; var oldValue = args.OldValue; var newValue = args.NewValue; if (!string.IsNullOrWhiteSpace(oldValue)) { clientSocket.cancelMktData(tickerId); } tickData = new TickData(); if (!string.IsNullOrWhiteSpace(newValue)) { tickerId = NumberGenerator.NextRandomInt(); tickerContract = ContractFactory.CreateStockContract(newValue); clientSocket.reqMktData(tickerId, tickerContract, "", false, null); } else { tickerId = -1; tickerContract = null; } }