private static void AdViewDidFailToReceiveAdWithErrorCallback(
            IntPtr bannerClient, string error)
        {
            BannerClient            client = IntPtrToBannerClient(bannerClient);
            AdFailedToLoadEventArgs args   = new AdFailedToLoadEventArgs()
            {
                Message = error
            };

            client.OnAdFailedToLoad(client, args);
        }
        private static void AdViewDidFailToReceiveAdWithErrorCallback(
            IntPtr bannerClient, IntPtr error)
        {
            BannerClient client = IntPtrToBannerClient(bannerClient);

            if (client.OnAdFailedToLoad != null)
            {
                LoadAdErrorClientEventArgs args = new LoadAdErrorClientEventArgs()
                {
                    LoadAdErrorClient = new LoadAdErrorClient(error)
                };
                client.OnAdFailedToLoad(client, args);
            }
        }