Meziantou.Framework

Getting started

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Install the package

Add the Meziantou.Framework.Scheduling package to your project:

dotnet package add Meziantou.Framework.Scheduling

The examples of this documentation omit the using directives: they need using Meziantou.Framework.Scheduling;.

The occurrences of a recurrence rule

Parse a rule, then enumerate its occurrences from the start of the series:

var rrule = "FREQ=WEEKLY;BYDAY=MO,WE;COUNT=10";
if (RecurrenceRule.TryParse(rrule, out var rule, out var error))
{
    var dtStart = new DateTime(2024, 01, 01, 09, 00, 00); // The DTSTART of the event
    var occurrences = rule.GetNextOccurrences(dtStart).ToArray();

    Assert.HasCount(10, occurrences);
    Assert.Equal(new DateTime(2024, 01, 01, 09, 00, 00), occurrences[0]); // Monday
    Assert.Equal(new DateTime(2024, 01, 03, 09, 00, 00), occurrences[1]); // Wednesday
    Assert.Equal(new DateTime(2024, 01, 31, 09, 00, 00), occurrences[9]);
}
else
{
    Assert.Fail(error);
}
  • TryParse returns false and the reason in error when the rule is not valid. Parse throws a FormatException instead.
  • The date you pass to GetNextOccurrences is the start of the series, the DTSTART of an iCalendar event: the first occurrences are computed from it, and the time of the occurrences comes from it. It is not "now": see The start of the series.
  • COUNT=10 ends the series after 10 occurrences. A rule without COUNT or UNTIL never ends: take the occurrences you need with Take or TakeWhile.

The next run of a cron expression

Parse an expression, then get the occurrences from now:

var cron = CronExpression.Parse("0 */15 * * * *");
var startDate = new DateTime(2024, 01, 01, 10, 05, 00); // DateTime.Now
var occurrences = cron.GetNextOccurrences(startDate).Take(10).ToArray();

Assert.HasCount(10, occurrences);
Assert.Equal(new DateTime(2024, 01, 01, 10, 15, 00), occurrences[0]);
Assert.Equal(new DateTime(2024, 01, 01, 10, 30, 00), occurrences[1]);

0 */15 * * * * has six fields, the first one being the seconds: second 0 of every 15th minute. The occurrences are on or after the date you pass; replace the fixed date with DateTime.Now in your application.

Next steps