string json = new WebClient().DownloadString("http://api.bitcoincharts.com/v1/weighted_prices.json");
            JObject jo = JObject.Parse(json);

            foreach (Currency c in db.Currencies.Where(x => x.Enabled))
            {
                if (c.FXRate == null) c.FXRate = new FXRate();
                c.FXRate.Value = Convert.ToDecimal(jo[c.ISO]["7d"].ToString());
                c.FXRate.EffectiveTs = DateTime.Now;
            }
            db.SaveChanges();