Dynamics 365 Business Central SaaS: save a file to an SFTP server

        [FunctionName("UploadFile")]
        public static async Task<IActionResult> Upload(
            [HttpTrigger(AuthorizationLevel.Function, "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
            dynamic data = JsonConvert.DeserializeObject(requestBody);

            string base64String = data.base64;
            string fileName = data.fileName;
            string fileType = data.fileType;
            string fileExt = data.fileExt;
            Uri uri = await UploadBlobAsync(base64String, fileName, fileType, fileExt);
            //Upload to SFTP
            fileName = await UploadFileToSFTP(uri, fileName);

            return fileName != null
                ? (ActionResult)new OkObjectResult($"File {fileName} stored. URI = {uri}")
                : new BadRequestObjectResult("Error on input parameter (object)");
        }

        public static async Task<Uri> UploadBlobAsync(string base64String, string fileName, string fileType, string fileExtension)
        {
            string contentType = fileType;
            byte[] fileBytes = Convert.FromBase64String(base64String);

            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(BLOBStorageConnectionString);
            CloudBlobClient client = storageAccount.CreateCloudBlobClient();
            CloudBlobContainer container = client.GetContainerReference("d365bcfiles");

            await container.CreateIfNotExistsAsync(
              BlobContainerPublicAccessType.Blob,
              new BlobRequestOptions(),
              new OperationContext());
            CloudBlockBlob blob = container.GetBlockBlobReference(fileName);
            blob.Properties.ContentType = contentType;

            using (Stream stream = new MemoryStream(fileBytes, 0, fileBytes.Length))
            {
                await blob.UploadFromStreamAsync(stream).ConfigureAwait(false);
            }

            return blob.Uri;
        }

        private static async Task<string> UploadFileToSFTP(Uri uri, string sourceFileName)
        {                        
            string storageAccountContainer = "d365bcfiles";            
            string storageConnectionString = BLOBStorageConnectionString;            
            string sourceFileAbsolutePath = uri.ToString();
            //SFTP Parameters (read it from configurations or Azure KeyVault)
            string sftpAddress = "YOUR FTP ADDRESS";
            string sftpPort = "YOUR FTP PORT";
            string sftpUsername = "YOUR FTP USERNAME";
            string sftpPassword = "YOUR FTP PASSWORD";
            string sftpPath = "YOUR FTP PATH";
            string targetFileName = sourceFileName;
            var memoryStream = new MemoryStream();

            CloudStorageAccount storageAccount;
            if (CloudStorageAccount.TryParse(storageConnectionString, out storageAccount))
            {
                CloudBlobClient cloudBlobClient = storageAccount.CreateCloudBlobClient();
                CloudBlobContainer cloudBlobContainer = cloudBlobClient.GetContainerReference(storageAccountContainer);
                
                CloudBlockBlob cloudBlockBlobToTransfer = cloudBlobContainer.GetBlockBlobReference(new CloudBlockBlob(uri).Name);
                await cloudBlockBlobToTransfer.DownloadToStreamAsync(memoryStream);
            }

            var methods = new List<AuthenticationMethod>();
            methods.Add(new PasswordAuthenticationMethod(sftpUsername, sftpPassword));

            //Connects to the SFTP Server and uploads the file 
            Renci.SshNet.ConnectionInfo con = new Renci.SshNet.ConnectionInfo(sftpAddress, sftpPort, new PasswordAuthenticationMethod(sftpUsername, sftpPassword));
            using (var client = new SftpClient(con))
            {
                client.Connect();
                client.UploadFile(memoryStream, $"/{sftpPath}/{targetFileName}");                
                client.Disconnect();
                return targetFileName;
            }

        }

    procedure UploadFile()
    var
        fileMgt: Codeunit "File Management";
        httpClient: HttpClient;
        httpContent: HttpContent;
        jsonBody: text;
        httpResponse: HttpResponseMessage;
        httpHeader: HttpHeaders;
        fileName: Text;
        fileExt: Text;
        InStr: InStream;
        base64Convert: Codeunit "Base64 Convert";
    begin
        UploadIntoStream('Select a file to upload', '', 'All files (*.*)|*.*', fileName, InStr);
        fileExt := fileMgt.GetExtension(fileName);

        jsonBody := ' {"base64":"' + base64Convert.ToBase64(InStr) +
        '","fileName":"' + fileName + '.' + fileExt +
        '","fileType":"' + GetMimeType(fileName) + '", "fileExt":"' + fileMgt.GetExtension(fileName) + 
            '"}';

        httpContent.WriteFrom(jsonBody);
        httpContent.GetHeaders(httpHeader);
        httpHeader.Remove('Content-Type');
        httpHeader.Add('Content-Type', 'application/json');
        httpClient.Post(BaseUrlUploadFunction, httpContent, httpResponse);
        //Here we should read the response to retrieve the URI
        message('File uploaded.');
    end;