A System.Theading.Timer example that waits for a long running process to finish

TimerTest.cs

using System;
using System.Threading;

public class TimerTest : IDisposable
{
    private readonly Timer _timer;
    private readonly object _locker = new object();

    public TimerTest()
    {
        _timer = new Timer(new TimerCallback(TickTimer), null, 1000, 1000);
    }

    private void TickTimer(object state)
    {
        // keep GC from collecting and stopping timer;
        GC.KeepAlive(_timer);

        // do not let another tick happen if we are still doing things - https://stackoverflow.com/a/13267259/2041
        if (Monitor.TryEnter(_locker))
        {
            try
            {
                // do long running work here
                DoWork();
            }
            finally
            {
                Monitor.Exit(_locker);
            }
        }
    }

    private void DoWork()
    {
        Console.WriteLine("Starting DoWork()");
        Thread.Sleep(2000);
        Console.WriteLine("Ending DoWork()");
    }
    
    public void Dispose()
    {      
        _timer?.Dispose();       
    }    
}