how to show display alert when httpClient.GetASync("uri") return response null ?

var httpClient = new HttpClient();
var response = await httpClient.GetAsync("url");

                if (response.StatusCode == HttpStatusCode.NoContent)
                {
                    await DisplayAlert("No Record!!", "No Record Found!! \n try another", "Cancel");
                }
                else
                {
                    var result = response.Content.ReadAsStringAsync().Result;
                    var name = JsonConvert.DeserializeObject<List<AddDonorClass>>(result);
                    LvDonors.ItemsSource = name;
                }