[c#] Repeating a function every few seconds

There are lot of different Timers in the .NET BCL:

• System.Timers.Timer
• System.Threading.Timer
• System.Windows.Forms.Timer
• System.Web.UI.Timer
• System.Windows.Threading.DispatcherTimer

When to use which?

• System.Timers.Timer, which fires an event and executes the code in one or more event sinks at regular intervals. The class is intended for use as a server-based or service component in a multithreaded environment; it has no user interface and is not visible at runtime.
• System.Threading.Timer, which executes a single callback method on a thread pool thread at regular intervals. The callback method is defined when the timer is instantiated and cannot be changed. Like the System.Timers.Timer class, this class is intended for use as a server-based or service component in a multithreaded environment; it has no user interface and is not visible at runtime.
• System.Windows.Forms.Timer (.NET Framework only), a Windows Forms component that fires an event and executes the code in one or more event sinks at regular intervals. The component has no user interface and is designed for use in a single-threaded environment; it executes on the UI thread.
• System.Web.UI.Timer (.NET Framework only), an ASP.NET component that performs asynchronous or synchronous web page postbacks at a regular interval.
• System.Windows.Threading.DispatcherTimer, a timer that's integrated into the Dispatcher queue. This timer is processed with a specified priority at a specified time interval.

Source

Some of them needs explicit Start call to begin ticking (for example System.Timers, System.Windows.Forms). And an explicit Stop to finish ticking.

using TimersTimer = System.Timers.Timer;

static void Main(string[] args)
{
    var timer = new TimersTimer(1000);
    timer.Elapsed += (s, e) => Console.WriteLine("Beep");
    Thread.Sleep(1000); //1 second delay
    timer.Start();
    Console.ReadLine();
    timer.Stop();

}

While on the other hand there are some Timers (like: System.Threading) where you don't need explicit Start and Stop calls. (The provided delegate will run a background thread.) Your timer will tick until you or the runtime dispose it.

So, the following two versions will work in the same way:

using ThreadingTimer = System.Threading.Timer;

static void Main(string[] args)
{
    var timer = new ThreadingTimer(_ => Console.WriteLine("Beep"), null, TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
    Console.ReadLine();
}

using ThreadingTimer = System.Threading.Timer;
static void Main(string[] args)
{
    StartTimer();
    Console.ReadLine();
}

static void StartTimer()
{
    var timer = new ThreadingTimer(_ => Console.WriteLine("Beep"), null, TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
}

But if your timer disposed then it will stop ticking obviously.

using ThreadingTimer = System.Threading.Timer; 

static void Main(string[] args)
{
    StartTimer();
    GC.Collect(0);
    Console.ReadLine();
}

static void StartTimer()
{
    var timer = new ThreadingTimer(_ => Console.WriteLine("Beep"), null, TimeSpan.FromSeconds(1), TimeSpan.FromSeconds(1));
}