public async Task <IEnumerable <ITicker> > MarketSummaries() { var prices = await _binance.GetPrices(); var pricesDic = prices.ToDictionary(p => p.symbol); var books = await _binance.GetBooks(); var tickersDic = books.ToDictionary(b => b.symbol); return(pricesDic.Keys.Select(k => new Market(pricesDic[k], tickersDic[k]))); }