does nulling a System.Threading.Timer stop it?

Question

If I have an active System.Threading.Timer and I set it to null, is it stopped?

I realize that it is more proper to call .Dispose() but I would like an answer to the question as written.

public class Foo
{
   private System.Threading.Timer _timer;
   public Foo()
   {
      // initialize timer
   }

   public void KillTimer()
   {
      _timer=null;
   }
}

---

Update:

After much back and forth about whether setting a single reference to a System.Threading.Timer to null will indeed result stopping it have shown that

1. there are no lingering references, e.g. events list, as a threading timer takes a sinlge callback and does not expose events.
2. that if GC collects, the finalizer will indeed dispose the TimerBase and stop the timer.

spike

using System;
using System.Threading;

namespace SO_3597276
{
    class Program
    {
        private static System.Threading.Timer _timer;

        static void Main(string[] args)
        {
            _timer = new Timer((s) => Console.WriteLine("fired"), null, 1000, Timeout.Infinite);
            _timer = null;
            GC.Collect();
            Console.ReadKey();
        }
    }
}

The timer callback is not called. Remove GC.Collect() and the callback is called.

Thanks all.

Answer 1

Why would it?

Consider:

  System.Threading.Timer t = ...;
  System.Threading.Timer q = t;
  q = null; // Should this stop it as well?

Setting to null is something you do to a variable, not something you do to an object. The Timer has no way of knowing you set a particular variable to null, and cannot take action on the basis of that.

EDIT:

To address the edit, even in the case of having a sole reference, it is not guaranteed that the Timer will be stopped, as it is possible the GC may not run after the reference has been set to null. This is not entirely unlikely either, the Microsoft .NET implementation uses a generational collector and a static field will likely survive a nursery collection and be promoted to an older generation. If your program has a relatively stable memory profile there may never be a collection of the older generations (and by extension the finalizer will not run until the end of the program).