private void ObserveSymbol(SymbolViewModel symbol)
        {
            var symbolObservable = Observable.FromEventPattern <SymbolEventArgs>(
                eventHandler => symbol.OnSymbolNotification += eventHandler,
                eventHandler => symbol.OnSymbolNotification -= eventHandler)
                                   .Select(eventPattern => eventPattern.EventArgs);

            var symbolObservableSubscription = symbolObservable.Subscribe(args =>
            {
                if (args.HasException)
                {
                    TradeViewModelException(args);
                }
            });

            symbolObservableSubscriptions.Add(symbol.Symbol.Name, symbolObservableSubscription);
        }
        private void ObserveSymbols()
        {
            var symbolsObservable = Observable.FromEventPattern <SymbolsEventArgs>(
                eventHandler => SymbolsViewModel.OnSymbolsNotification += eventHandler,
                eventHandler => SymbolsViewModel.OnSymbolsNotification -= eventHandler)
                                    .Select(eventPattern => eventPattern.EventArgs);

            symbolsObservableSubscription = symbolsObservable.Subscribe(async(args) =>
            {
                if (args.HasException)
                {
                    TradeViewModelException(args);
                }
                else if (args.Value != null)
                {
                    var symbol = Symbols.FirstOrDefault(s => s.Symbol.Name.Equals(args.Value.Name));
                    if (symbol != null)
                    {
                        SelectedSymbol = symbol;
                    }
                    else
                    {
                        symbol            = new SymbolViewModel(exchangeService, chartHelper, userAccount.Preferences, Logger);
                        symbol.Dispatcher = ViewModelContext.UiDispatcher;
                        Symbols.Add(symbol);
                        SelectedSymbol = symbol;

                        try
                        {
                            await symbol.SetSymbol(args.Value);
                            ObserveSymbol(symbol);
                        }
                        catch (Exception ex)
                        {
                            TradeViewModelException(ex.ToString(), ex);
                        }
                    }
                }
                else if (args.Symbols != null)
                {
                    TradeViewModel.SetSymbols(args.Symbols);
                }
            });
        }