Define scheduled tasks in C#

Question

I know that there are a lot of questions (and respectfully answers) related to this topic on this site, but as I am a newbie to C#, I still cannot figure out which solution works for me and that is why I decided to describe my situation here.

I write an application, which starts with the main method:

class Program
{
   static void Main(string[] args)
   {
   }
}

In this main method, I have to implement checking for new folders every 10 minutes.

I have another class defined for that - NewFoldersChecker, and static method in it "CheckForNewFolders"....so I hoped that a method in the class Program like this:

        private static void CheckForNewFolders()
        {
            Task.Run(async () =>
            {
                while (true)
                {
                    NewFoldersChecker.CheckForNewFolders();
                    await Task.Delay(60000);
                }


            });
        }

and calling it from the main method would do the job:

        static void Main(string[] args)
        {
            CheckForNewFolders();
        }

But obviously, this is not the case - the method is called once and that is all because the main thread ends.

What should I do to keep the main thread alive or what are my other options?

Have a look at https://learn.microsoft.com/en-us/dotnet/api/system.io.filesystemwatcher?view=net-6.0 instead of polling every X. — Preben Huybrechts, Aug 16 '22 at 12:08
Is there a reason why CheckForNewFolders isn't async itself? — gunr2171, Aug 16 '22 at 12:08
@ArthurAttout Using `.Wait` is almost always a terrible idea, as it is here. — DavidG, Aug 16 '22 at 12:09
Why is it so ? It looks like a console application in this case, so I don't really get why it would be that much an issue. Doesn't `async main` wrap it this way anyways ? — Arthur Attout, Aug 16 '22 at 12:11
The problem is that your main method calls `CheckForNewFolders` but doesn't wait for it, so your app just ends. — DavidG, Aug 16 '22 at 12:11
This seems like an [X/Y problem](https://xyproblem.info/). If you want something to run every 10 minutes exactly, use Windows Task Scheduler and Cron, or an in-process scheduling library. If you want to trigger an event on file system modification, go with Preben's comment. — gunr2171, Aug 16 '22 at 12:12
Many questions arise, is there a reason you need to implement a scheduled task rather than a FileSystemWatcher? Is there a reason you need to do a Console application rather than a Windows Service a WebJob or a Web Application? Depending on the answers you will find multiple options for your implementation. — Mauricio Atanache, Aug 16 '22 at 12:14
@DavidG Stephen Cleary actually suggests exactly that in [this post](https://stackoverflow.com/a/17630538/7540393). — Arthur Attout, Aug 21 '22 at 13:52
@ArthurAttout And he wrote that in 2013, long before we had async main in C# — DavidG, Aug 21 '22 at 18:30
And that question is already marked as a duplicate of https://stackoverflow.com/questions/9208921/cant-specify-the-async-modifier-on-the-main-method-of-a-console-app which tells you how to use async Main — DavidG, Aug 21 '22 at 18:31

score 4 · Answer 1 · answered Aug 16 '22 at 12:12

I would highly recommend using a timer instead. These are made for running things periodically. Your Task.Delay is just a wrapper around a timer set to trigger a single time, so you are just making things more complicated for yourself.

For example:

static void Main(string[] args)
{
    using var aTimer = new System.Timers.Timer(60000);
    aTimer.Elapsed += OnTimedEvent;
    aTimer.AutoReset = true;
    aTimer.Enabled = true;

    Console.WriteLine("Checking folders. press any key to exit");
    Console.ReadKey();
}
private static void OnTimedEvent(Object source, ElapsedEventArgs e)
{
    // Check your folders here
}

Define scheduled tasks in C#

1 Answers1