ISchedulerFactory sf = new StdSchedulerFactory();
            IScheduler sched = sf.GetScheduler();
            JobDetail job = new JobDetail("job1", "group1", typeof(JobExecute));
            CronTrigger trigger = new CronTrigger("trigger1", "group1", "job1", "group1");
            //二十秒执行一次 :0/20 * * * * ?
            int hh = Convert.ToInt32(TextHH.Text);
            int mm = Convert.ToInt32(TextMM.Text);
            trigger.CronExpressionString = "0 " + mm + " " + hh + " * * ?";
            sched.AddJob(job, true);
            DateTime ft = sched.ScheduleJob(trigger);
            sched.Start();出异常:Unable to store Trigger with name: 'trigger1' and group: 'group1', because one already exists with this identification.