Polly - Back Off and Retry on Error http client

retry.cs

//Retry http with a back off on failure

 await Policy.Handle<HttpRequestException>().WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)))
                .ExecuteAsync(async () =>
                {
                    var result = await httpClient.GetAsync("api/CallToServer/" + varibleToSendToServer, cancellationToken);
                    if (result.IsSuccessStatusCode)
                    {
                        returnValue = await result.Content.ReadAsAsync<List<Results>>(token);
                    }
                    else if (result.StatusCode == HttpStatusCode.Unauthorized)
                    {
                        throw new UnauthorizedAccessException("Your Session has expired.");
                    }
                });