.NET SDK Background Service that can use CRON notation to run periodically.

CrontabService.cs

public abstract class CrontabService : BackgroundService
    {
        private DateTime nextRun;

        private readonly CrontabSchedule _schedule;
        private readonly ILogger _logger;

        public CrontabService(CrontabSchedule schedule, ILogger logger)
        {
            _schedule = schedule;
            nextRun = _schedule.GetNextOccurrence(DateTime.Now);
            _logger = logger;
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            do
            {
                var now = DateTime.Now;
                _logger.LogInformation("Next run at: " + nextRun);
                if (now > nextRun)
                {
                    _logger.LogInformation("Running scheduled task.");
                    await Process(stoppingToken);
                    nextRun = _schedule.GetNextOccurrence(DateTime.Now);
                }
                await Task.Delay(TimeSpan.FromSeconds(15), stoppingToken);
            }
            while (!stoppingToken.IsCancellationRequested);
        }

        protected abstract Task Process(CancellationToken stoppingToken);
    }