Timer configuration

Question

protected void StartFunction()
  {	 
	 ReqTimer = new System.Threading.Timer((o) =>
    {
	   // for one and two nort needed, right?
       // if (ReqTimer != null)
       //     ReqTimer.Change(1000 * 15, Timeout.Infinite);   

    }, null, 1000 * 15, System.Threading.Timeout.Infinite);
  }

Can someone please help me. I would like to map the three variants.

Timer only starts in x seconds Timer starts immediately Timer only starts in x seconds and makes an interval every n seconds.

How do I have to program this? Preferably with and without lambda (easier to read)

Answer 1

unlike the system.timer class which runs the callback on the same thread, the System.Threading runs the callback on a thread from the thread pool.

using System;
using System.Threading;

var n = 3; // n seconds
var counter = 0; // non thread safe counter
var locker = new object(); // object to lock on

// timer fire once now
var timer1 = new Timer(
	callback: new TimerCallback(TimerProc),
	state: "timer1",        // state
	dueTime: 0,             // start with no delay
	period: Timeout.Infinite // only once
);
// timer fire only once after n seconds
var timer2 = new Timer(
	callback: new TimerCallback(TimerProc),
	state: "timer2",        // state
	dueTime: n * 1000,      // start in 1 second
	period: Timeout.Infinite // only once
);
// timer fire only once after n seconds
var timer3 = new Timer(
	callback: new TimerCallback(TimerProc),
	state: "timer3",        // state
	dueTime: n * 1000,      // start in 1 seconds
	period: 10 * 1000       // repeat every 10 seconds
);

// delay main thread until timer thread complete
Thread.Sl eep(35000);
timer3.Dispose(); // cancel running timer
Console.WriteLine("all done");

void TimerProc(object? state)
{
    var t = 0;
    lock (locker)
    {
        // simulate non threadsafe  work
        var a = counter;
        Thread.Sl eep(1000);
        counter = a + 1;
        t = counter;
    }
	Console.WriteLine($"{state}: counter: {t} thread: {Thread.CurrentThread.ManagedThreadId}");
}

note: because thread2 and thread3 start at the same time, its undefined which runs and completes first.