how many threads are used by one Threading.Timer ?

Hi,

I like to know how many threads are used by a Threading.Timer object.
When I create a Threading.Timer object calling a short running method
every 5 seconds I expected to have one additional ThreadPool thread.
And that is exactly what MS VIsual Studio shows.

But when I run Processexplorer or Taskmanager I see 2 additional
threads, after a while another 2 additional threads. With the 3 threads
at start time we have totally 7 threads.
Please follow the code below to get the locations of the threads.
Does anyone know

1. Where do the three start threads come from (UI thread, GC?, and ?)

2. Does the timer itself consumes permanently a thread? Not only the
method he invokes? This would explain why we get two additional
threads.
If yes, is it a ThreadPool thread?

3. Why do we see another pair of additional threads?

4. Is it dangerous to use many Threading.Timer objects (even for
shortrunning methods)=

// program to demonstrate thread usage by Threading.Timer
using System;
using System.Threadin g;
namespace NS_ThreadingTim er
{
class TimerState
{
public int counter = 0; // thread parameter
public volatile Timer tmr; // timer reference needed for disposing
}
class App
{
public static void Main()
{
Console.WriteLi ne("starting timer, press ENTER ...");
Console.ReadLin e();
// VisualStudio shows here one thread:
// NS_ThreadingTim er.App.Main (location)
// ProcessExplorer and TaskManager shows here 3 threads:
// mscoree.dll!_Co rExeMain
// mscorwks.dll!De buggerRCThread: :ThreadProcStat ic
// mscorwks.dll!Th read::intermedi ateThreadProc
// start timer immediately, then invoke CheckStatus every 5
seconds.
TimerState s = new TimerState();
TimerCallback timerDelegate = new TimerCallback (CheckStatus);
Timer timer = new Timer (timerDelegate, s, 0, 5000);
s.tmr = timer; // Keep handle to timer, so it can be disposed.
while (s.tmr != null) // Main thread NOP until timer is disposed.
Thread.Sleep(10 00);
// VisualStudio shows 2 threads:
// NS_ThreadingTim er.App.Main (location)
// System.IO.__Con soleStream.Read FileNative
// ProcessExplorer and TaskManager shows here 7 threads:
// mscoree.dll!_Co rExeMain
// mscorwks.dll!De buggerRCThread: :ThreadProcStat ic
// mscorwks.dll!Th read::intermedi ateThreadProc
// mscorwks.dll!Th readpoolMgr::Ti merThreadStart
// mscorwks.dll!Th readpoolMgr::in termediateThrea dProc
// mscorwks.dll!Th readpoolMgr::in termediateThrea dProc
// mscorwks.dll!Th readpoolMgr::Ga teThreadStart
Console.WriteLi ne("Timer example done, press ENTER to continue
...");
Console.ReadLin e();
}
static void CheckStatus(Obj ect state)
{
// VisualStudio shows 2 threads:
// NS_ThreadingTim er.App.Main (location)
// NS_ThreadingTim er.App.CheckSta tus (location)
// ProcessExplorer and TaskManager shows here 7 threads:
// mscoree.dll!_Co rExeMain
// mscorwks.dll!De buggerRCThread: :ThreadProcStat ic
// mscorwks.dll!Th read::intermedi ateThreadProc
// mscorwks.dll!Th readpoolMgr::Ti merThreadStart
// mscorwks.dll!Th readpoolMgr::in termediateThrea dProc
// mscorwks.dll!Th readpoolMgr::in termediateThrea dProc
// mscorwks.dll!Th readpoolMgr::Ga teThreadStart
TimerState s =(TimerState) state;
s.counter++;
Console.WriteLi ne("{0}: {1}.", DateTime.Now.Ti meOfDay,
s.counter);
if (s.counter == 10)
{
s.tmr.Dispose() ;
s.tmr = null;
}
}
}
}
So many questions, but I could not find the answer out of the docs.

Greetings,
Michael Heitland

Hi Willy,

thanx for your quick reply.

Now it became clearer to me, but some questions are still left:
1. what is the IOC thread (IO control?)?
2. Is the IOC thread a threadpool thread? May I run into resource
problems, if I use more than 25 Threading.Timer objects (the threadpool
is limited to 25 threads per processor in .NET 1.1)?
3. Why do I see another pair of threads after a while?
4. Is the gate thread also a ThreadPool thread?

Michael