private async Task GetCompletedCheckoutAsync()
        {
            UIApplication.SharedApplication.NetworkActivityIndicatorVisible = true;

            try
            {
                this.Checkout = await client.GetCheckoutAsync(this.Checkout);

                Console.WriteLine(Checkout);
            }
            catch (NSErrorException ex)
            {
                Console.WriteLine("Unable to get completed checkout: {0}", ex.Error);
            }

            UIApplication.SharedApplication.NetworkActivityIndicatorVisible = false;
        }