ファイル送信 リトライ付き

        private static bool RetryInProgress { get; set; } = false;

        public static async Task UploadFileWithRetryAsync()
        {
            Console.WriteLine($"Start UploadFileWithRetryAsync");

            if (RetryInProgress)
            {
                Console.WriteLine($"Retrying");

                return;
            }

            RetryInProgress = true;

            for (int i = 0; i < 7; i++)
            {
                if (i != 0)
                {
                    int waitTimeInSeconds = (int)Math.Pow(2, i - 1);

                    Console.WriteLine($"Waiting for {waitTimeInSeconds} seconds...");

                    await Task.Delay(TimeSpan.FromSeconds(waitTimeInSeconds));
                }

                try
                {
                    Console.WriteLine($"Trying {i + 1}");

                    using (var stream = new FileStream(LocalFilePath, FileMode.Open))
                    {
                        await UploadFileAsync(stream, RemoteFileName);

                        break;
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"Error: {ex.Message}");
                }
            }

            RetryInProgress = false;

            Console.WriteLine($"End UploadFileWithRetryAsync");
        }