Crontab.Scheduler 1.0.0

Cron Expression Scheduler for .Net

A .Net scheduler using cron expressions built on top of NCrontab by atifaziz

How to install?

You can find the library on nuget.org by searching for NCrontabScheduler

How to inject the scheduler?

You have to call the .AddCronScheduler() on your service collection. Once done, you can directly inject the ICronScheduler interface in your desired class to use it.

Example:

IServiceProvider BuildServiceProvider() => new ServiceCollection()
    .AddCronScheduler()
    .BuildServiceProvider();

How to use?

In general, you have to call the ScheduleJob method using the instance of ICronScheduler you injected. This method takes only one argument of type ISchedulerOptions. The library comes with a builder to make it easier to prepare this parameter.

Current options included:

• CronExpression - required.
• StartDate - optional - Now by default
• EndDate - optional - Now + 1 year by default
• NumberOfTimesToExecute - optional - null by default
• One of the two next options is required, and can't have both:
  • CronExecutor
  • ActionToExecute

SchedulerOptionsBuilder

The builder is straightforward to use. For example:

new SchedulerOptionsBuilder("* * * * *")
    .WithEndDate(DateTime.Now.AddMinutes(2)) 
    .WithActionToExecute(() => Console.WriteLine($"{DateTime.Now}: Hello from an action!"))
    .WithNumberOfTimesToExecute(3)
    .Build()

Cron expressions format:

Five-part format without seconds:

* * * * *
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday=0)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)

or a six-part format that allows for seconds:

* * * * * *
- - - - - -
| | | | | |
| | | | | +--- day of week (0 - 6) (Sunday=0)
| | | | +----- month (1 - 12)
| | | +------- day of month (1 - 31)
| | +--------- hour (0 - 23)
| +----------- min (0 - 59)
+------------- sec (0 - 59)

Start and End date:

When specified, the scheduler will only execute your desired function between these two dates.

Number of times to execute:

Regardless of how many occurences the scheduler finds between start and end date, it will only execute the desired function as much as specified.

Cron Executor

To use an executor, you have to implement the interface ICronExecutor and implement the function Execute. For example:

public class MyExecutor : ICronExecutor
{
    public void Execute()
    {
        Console.WriteLine($"{DateTime.Now}: Hello From Executor!");
    }
}

Then you pass an instance of this executor to the builder using the function WithCronExecutor(executor).

Action to execute

If you want a quick action to be executed without the need to implement the interface, you can use an action such as: .WithActionToExecute(() => Console.WriteLine($"{DateTime.Now}: Hello from an action!"))

How to follow executions?

When you call ScheduleJob, an instance of ICronJob is returned (if successful). Four events can be listened to:

• OnJobExecuted - Fires after an action or an executor being successfully executed.
• OnJobNoMoreOccurrences - Fires when the scheduler can no longer find any occurrences between start and end date.
• OnJobMaxExecution - Fires when the scheduler reaches the maximum number to execute (if provided)
• OnErrorExecuting - Fires when an exception is caught during executing.