An Example Crypto API Service to use as an external Datasource

CryptoService.cs

namespace FluxDigital.Sitecore.Extensions.Services
{
    public class CryptoService
    {
        public List<CryptoCoin> CointList()
        {
            List<CryptoCoin> coinList = new List<CryptoCoin>();
            HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create("https://www.cryptocompare.com/api/data/coinlist/");
            httpWebRequest.ContentType = "application/json";
            httpWebRequest.Method = "GET";
            using (HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse())
            using (Stream stream = httpWebResponse.GetResponseStream())
            using (StreamReader reader = new StreamReader(stream))
            {
                var result = reader.ReadToEnd();
                var cryptoResponse = JsonConvert.DeserializeObject<RootCryptoResponse>(result);
                if (cryptoResponse != null)
                {
                    coinList = cryptoResponse.Coins.Values.ToList<CryptoCoin>();
                }
            }
            return coinList;
        }
    }
}