public async Task ReadSalesSumAsync()
        {
            try
            {
                var credentials = new NetworkCredential("user", "pwrd", "domain");
                using FtpClient client = new FtpClient(ftpAddress,21, credentials);             
                await client.ConnectAsync();
                await client.SetWorkingDirectoryAsync("/folder");
                var fileList = await client.GetListingAsync();
				
                foreach (var item in fileList)
                {
                    if (item.Type== FtpFileSystemObjectType.File && item.Name.Substring(item.Name.Length - 3, 3).ToUpper().Equals("XML"))
                    {
                        await parseXml(item.FullName, client);
                    }
                }
                await client.DisconnectAsync();
            }
            catch (Exception ex)
            {            
                throw;
            }

            //Парсинг XML-файла
            async Task parseXml(string filePath, FtpClient client)
            {
                using (var stream = await client.OpenReadAsync(filePath))
                {
                    using (var reader= new StreamReader(stream))
                    {
                        var content =await reader.ReadToEndAsync();
                    }
                }
            }
        }

using (var stream = await client.OpenReadAsync(filePath))

using (var stream = await client.OpenReadAsync(filePath))
       {
         try
         {                    
         }
         finally  
         {
            stream.Close();
         }
      }