title: quartz.net cron trigger
body: <p>i have a problem with using cron trigger in Quartz.net. My code:</p>
  
  <pre><code>        var trigger = new CronTrigger("0/30 * * * * ?");
  
          trigger.Name = "some name";
          trigger.Group = "group";
  
          scheduler.ScheduleJob(jobDetails, trigger);
  </code></pre>
  
  <p>it should run every 30 seconds, but on last line following exception occures:
  "Based on configured schedule, the given trigger will never fire."
  can anyone help?</p>