Develop Reference

C# How to pause a timer?

I have a C# program in which, I need the timer to stop if the user stops interacting with the program. What It needs to do is pause, and then restart when the user becomes active again. I have done some research, and found that there is commands such as:
timer.Stop();
and
timer.Start();
But I was wondering if there was like a:
timer.Pause();
And then when the user becomes active again, it picks up where it left off, and doesn't restart. If anyone can help, it would be much appreciated!
Thanks,
Micah

You achieve this by using the Stopwatch class in .NET. By simply stopping and starting you continue the use of the instance of the stopwatch.
Make sure to make use of using System.Diagnostics;
var timer = new Stopwatch();
timer.Start();
timer.Stop();
Console.WriteLine(timer.Elapsed);
timer.Start(); //Continues the timer from the previously stopped time
timer.Stop();
Console.WriteLine(timer.Elapsed);
To reset the stopwatch, just call the Reset or Restart methods, like below:
timer.Reset();
timer.Restart();

I have created this class for this situation:
public class PausableTimer : Timer
{
public double RemainingAfterPause { get; private set; }
private readonly Stopwatch _stopwatch;
private readonly double _initialInterval;
private bool _resumed;
public PausableTimer(double interval) : base(interval)
{
_initialInterval = interval;
Elapsed += OnElapsed;
_stopwatch = new Stopwatch();
}
public new void Start()
{
ResetStopwatch();
base.Start();
}
private void OnElapsed(object sender, ElapsedEventArgs elapsedEventArgs)
{
if (_resumed)
{
_resumed = false;
Stop();
Interval = _initialInterval;
Start();
}
ResetStopwatch();
}
private void ResetStopwatch()
{
_stopwatch.Reset();
_stopwatch.Start();
}
public void Pause()
{
Stop();
_stopwatch.Stop();
RemainingAfterPause = Interval - _stopwatch.Elapsed.TotalMilliseconds;
}
public void Resume()
{
_resumed = true;
Interval = RemainingAfterPause;
RemainingAfterPause = 0;
Start();
}
}

There is not a pause because it is easy to do the equivalent. You can just stop the timer instead of pausing it, then when you need to restart it you just need to specify the amount of time remaining. It might be complicated or it might be simple; it depends on what you are using the timer to do. The fact that what you do depends on what you are using the timer for is probably the reason a pause does not exist.
You might be using the timer to do something repetitively at a regular time period or you might be using the timer to count down to a specific time. If you are doing something (such as every second) repetitively then your requirements might be to restart at the beginning of that time period (a second) or at a portion of that period. What happens if the pause is for more than the time period? Usually the missed events would be ignored but that depends on requirements.
So I am trying to say that you need to determine your requirements. Then if you need help then clarify what you need.

Reliably stop System.Threading.Timer?

Well I've searched a lot for a solution to this. I'm looking for a clean and simple way to prevent the callback method of a System.Threading.Timer from being invoked after I've stopped it.
I can't seem to find any, and this has led me, on occassion, to resort to the dreaded thread-thread.sleep-thread.abort combo.
Can it be done using lock?

An easier solution might to be to set the Timer never to resume; the method Timer.Change can take values for dueTime and period that instruct the timer never to restart:
this.Timer.Change(Timeout.Infinite, Timeout.Infinite);
Whilst changing to use System.Timers.Timer might be a "better" solution, there are always going to be times when that's not practical; just using Timeout.Infinite should suffice.

like Conrad Frix suggested you should use the System.Timers.Timer class instead, like:
private System.Timers.Timer _timer = new System.Timers.Timer();
private volatile bool _requestStop = false;
public constructor()
{
_timer.Interval = 100;
_timer.Elapsed += OnTimerElapsed;
_timer.AutoReset = false;
_timer.Start();
}
private void OnTimerElapsed(object sender, System.Timers.ElapsedEventArgs e)
{
// do work....
if (!_requestStop)
{
_timer.Start();//restart the timer
}
}
private void Stop()
{
_requestStop = true;
_timer.Stop();
}
private void Start()
{
_requestStop = false;
_timer.Start();
}

The MSDN Docs suggest that you use the Dispose(WaitHandle) method to stop the timer + be informed when callbacks will no longer be invoked.

For the System.Threading.Timer one can do the following (Will also protect the callback-method from working on a disposed timer - ObjectDisposedException):
class TimerHelper : IDisposable
{
private System.Threading.Timer _timer;
private readonly object _threadLock = new object();
public event Action<Timer,object> TimerEvent;
public void Start(TimeSpan timerInterval, bool triggerAtStart = false,
object state = null)
{
Stop();
_timer = new System.Threading.Timer(Timer_Elapsed, state,
System.Threading.Timeout.Infinite, System.Threading.Timeout.Infinite);
if (triggerAtStart)
{
_timer.Change(TimeSpan.FromTicks(0), timerInterval);
}
else
{
_timer.Change(timerInterval, timerInterval);
}
}
public void Stop(TimeSpan timeout = TimeSpan.FromMinutes(2))
{
// Wait for timer queue to be emptied, before we continue
// (Timer threads should have left the callback method given)
// - http://woowaabob.blogspot.dk/2010/05/properly-disposing-systemthreadingtimer.html
// - http://blogs.msdn.com/b/danielvl/archive/2011/02/18/disposing-system-threading-timer.aspx
lock (_threadLock)
{
if (_timer != null)
{
ManualResetEvent waitHandle = new ManualResetEvent(false)
if (_timer.Dispose(waitHandle))
{
// Timer has not been disposed by someone else
if (!waitHandle.WaitOne(timeout))
throw new TimeoutException("Timeout waiting for timer to stop");
}
waitHandle.Close(); // Only close if Dispose has completed succesful
_timer = null;
}
}
}
public void Dispose()
{
Stop();
TimerEvent = null;
}
void Timer_Elapsed(object state)
{
// Ensure that we don't have multiple timers active at the same time
// - Also prevents ObjectDisposedException when using Timer-object
// inside this method
// - Maybe consider to use _timer.Change(interval, Timeout.Infinite)
// (AutoReset = false)
if (Monitor.TryEnter(_threadLock))
{
try
{
if (_timer==null)
return;
Action<Timer, object> timerEvent = TimerEvent;
if (timerEvent != null)
{
timerEvent(_timer, state);
}
}
finally
{
Monitor.Exit(_threadLock);
}
}
}
}
This is how one can use it:
void StartTimer()
{
TimerHelper _timerHelper = new TimerHelper();
_timerHelper.TimerEvent += (timer,state) => Timer_Elapsed();
_timerHelper.Start(TimeSpan.FromSeconds(5));
System.Threading.Sleep(TimeSpan.FromSeconds(12));
_timerHelper.Stop();
}
void Timer_Elapsed()
{
// Do what you want to do
}

For what it's worth, we use this pattern quite a bit:
// set up timer
Timer timer = new Timer(...);
...
// stop timer
timer.Dispose();
timer = null;
...
// timer callback
{
if (timer != null)
{
..
}
}

This answer relates to System.Threading.Timer
I've read a lot of nonsense about how to synchronize disposal of System.Threading.Timer all over the net. So that's why I'm posting this in an attempt to rectify the situation somewhat. Feel free to tell me off / call me out if something I'm writing is wrong ;-)
Pitfalls
In my opinion there's these pitfalls:
Timer.Dispose(WaitHandle) can return false. It does so in case it's already been disposed (I had to look at the source code). In that case it won't set the WaitHandle - so don't wait on it!
not handling a WaitHandle timeout. Seriously - what are you waiting for in case you're not interested in a timeout?
Concurrency issue as mentioned here on msdn where an ObjectDisposedException can occur during (not after) disposal.
Timer.Dispose(WaitHandle) does not work properly with -Slim waithandles, or not as one would expect. For example, the following does not work (it blocks forever):
using(var manualResetEventSlim = new ManualResetEventSlim)
{
timer.Dispose(manualResetEventSlim.WaitHandle);
manualResetEventSlim.Wait();
}
Solution
Well the title is a bit "bold" i guess, but below is my attempt to deal with the issue - a wrapper which handles double-disposal, timeouts, and ObjectDisposedException. It does not provide all of the methods on Timer though - but feel free to add them.
internal class Timer
{
private readonly TimeSpan _disposalTimeout;
private readonly System.Threading.Timer _timer;
private bool _disposeEnded;
public Timer(TimeSpan disposalTimeout)
{
_disposalTimeout = disposalTimeout;
_timer = new System.Threading.Timer(HandleTimerElapsed);
}
public event Action Elapsed;
public void TriggerOnceIn(TimeSpan time)
{
try
{
_timer.Change(time, Timeout.InfiniteTimeSpan);
}
catch (ObjectDisposedException)
{
// race condition with Dispose can cause trigger to be called when underlying
// timer is being disposed - and a change will fail in this case.
// see
// https://msdn.microsoft.com/en-us/library/b97tkt95(v=vs.110).aspx#Anchor_2
if (_disposeEnded)
{
// we still want to throw the exception in case someone really tries
// to change the timer after disposal has finished
// of course there's a slight race condition here where we might not
// throw even though disposal is already done.
// since the offending code would most likely already be "failing"
// unreliably i personally can live with increasing the
// "unreliable failure" time-window slightly
throw;
}
}
}
private void HandleTimerElapsed(object state)
{
Elapsed?.Invoke();
}
public void Dispose()
{
var waitHandle = new ManualResetEvent(false));
// returns false on second dispose
if (_timer.Dispose(waitHandle))
{
if (waitHandle.WaitOne(_disposalTimeout))
{
_disposeEnded = true;
waitHandle.Dispose();
}
else
{
// don't dispose the wait handle, because the timer might still use it.
// Disposing it might cause an ObjectDisposedException on
// the timer thread - whereas not disposing it will
// result in the GC cleaning up the resources later
throw new TimeoutException(
"Timeout waiting for timer to stop. (...)");
}
}
}
}

You can't guarantee that your code that supposed to stop the timer will execute before timer event invocation.
For example, suppose on time moment 0 you initialized timer to call event when time moment 5 comes. Then on time moment 3 you decided that you no longer needed the call. And called method you want to write here. Then while method was JIT-ted comes time moment 4 and OS decides that your thread exhaust its time slice and switch. And timer will invoke the event no matter how you try - your code just won't have a chance to run in worst case scenario.
That's why it is safer to provide some logic in the event handler. Maybe some ManualResetEvent that will be Reset as soon as you no longer needed event invocation. So you Dispose the timer, and then set the ManualResetEvent. And in the timer event handler first thing you do is test ManualResetEvent. If it is in reset state - just return immediately. Thus you can effectively guard against undesired execution of some code.

To me, this seems to be the correct way to go:
Just call dispose when you are done with the timer. That will stop the timer and prevent future scheduled calls.
See example below.
class Program
{
static void Main(string[] args)
{
WriteOneEverySecond w = new WriteOneEverySecond();
w.ScheduleInBackground();
Console.ReadKey();
w.StopTimer();
Console.ReadKey();
}
}
class WriteOneEverySecond
{
private Timer myTimer;
public void StopTimer()
{
myTimer.Dispose();
myTimer = null;
}
public void ScheduleInBackground()
{
myTimer = new Timer(RunJob, null, 1000, 1000);
}
public void RunJob(object state)
{
Console.WriteLine("Timer Fired at: " + DateTime.Now);
}
}

Perhaps you should do the opposite. Use system.timers.timer, set the AutoReset to false and only Start it when you want to

You can stop a timer by creating a class like this and calling it from, for example, your callback method:
public class InvalidWaitHandle : WaitHandle
{
public IntPtr Handle
{
get { return InvalidHandle; }
set { throw new InvalidOperationException(); }
}
}
Instantiating timer:
_t = new Timer(DisplayTimerCallback, TBlockTimerDisplay, 0, 1000);
Then inside callback method:
if (_secondsElapsed > 80)
{
_t.Dispose(new InvalidWaitHandle());
}

There is a MSDN link how to achieve stop timer correctly. Use ControlThreadProc() method with HandleElapsed(object sender, ElapsedEventArgs e) event synchronized by syncPoint static class variable. Comment out Thread.Sleep(testRunsFor); on ControlThreadProc() if it is not suitable(probably).
The key is there that using static variable and an atomic operation like Interlocked.CompareExchange on conditional statements.
Link :
Timer.Stop Method

Non-reentrant C# timer

I'm trying to invoke a method f() every t time, but if the previous invocation of f() has not finished yet, wait until it's finished.
I've read a bit about the available timers but couldn't find any good way of doing what I want, save for manually writing it all. Any help about how to achieve this will be appreciated, though I fear I might not be able to find a simple solution using timers.
To clarify, if t is one second, and f() runs the arbitrary durations I've written below, then:
Step Operation Time taken
1 wait 1s
2 f() 0.6s
3 wait 0.4s (because f already took 0.6 seconds)
4 f() 10s
5 wait 0s (we're late)
6 f() 0.3s
7 wait 0.7s (we can disregard the debt from step 4)
Notice that the nature of this timer is that f() will not need to be safe regarding re-entrance, and a thread pool of size 1 is enough here.

Use a System.Threading.Timer. Initialize it with a period of Timeout.Infinite so it acts like a one-shot timer. When f() completes, call its Change() method to recharge it again.

You could just use a 'global' level var (or more likely, a public property in the same class as f()) which returns true if f() is already running.
So if f() was in a class named TimedEvent, the first thing f() would do is set Running true
That way your timer fires every second, then launches the timed event if it isnt already running
if (!timedEvent.Running) timedEvent.f()
You commented that f() wouldnt repeat immediately if it took longer than the timer interval. Thats a fair point. I would probably include logic like that inside f() so that Running stays true. So it would look something like this:
public void f(int t) // t is interval in seconds
{
this.running = true;
Stopwatch stopWatch = new Stopwatch();
stopWatch.Start();
do
{
stopwatch.Reset();
// Do work here
} while (stopWatch.Elapsed.Seconds > t); // repeat if f() took longer than t
this.running = false;
}

You can use a non-restarting timer, then manually restart the timer after the method finishes.
Note that this will result in timing that is somewhat different from what you're asking for. (There will always be a gap of t time between invocations)
You could solve that by setting the interval to lastTick + t - Now, and running the method immediately if that's <= 0.
Beware of race conditions if you need to stop the timer.

You cannot get a timer to call you at exactly scheduled intervals. All timers do is call you back no sooner than the requested time.
Some timers are better than others (e.g. Windows.Forms.Timer is very erratic and unreliable compared to System.Threading.Timer)
To stop your timer being called re-entrantly, one approach is to Stop the timer while your method is running. (Depending on the type of timer you use, you either stop it and start it again when your handler exits, or with some timers you can request a single callback rather than repeating callbacks, so each execution of your handler simply enqueues the next call).
To keep the timing relatively even between these calls you can record the time since your handler last executed and use that to calculate the delay until the next event is required. e.g. If you want to be called once per second and your timer completed provcessing at 1.02s, then you can set up the next timer callback at a duration of 0.98s to accomodate the fact that you've already "used up" part of the next second during your processing.

A straightforward solution:
private class Worker : IDisposable
{
private readonly TimeSpan _interval;
private WorkerContext _workerContext;
private sealed class WorkerContext
{
private readonly ManualResetEvent _evExit;
private readonly Thread _thread;
private readonly TimeSpan _interval;
public WorkerContext(ParameterizedThreadStart threadProc, TimeSpan interval)
{
_evExit = new ManualResetEvent(false);
_thread = new Thread(threadProc);
_interval = interval;
}
public ManualResetEvent ExitEvent
{
get { return _evExit; }
}
public TimeSpan Interval
{
get { return _interval; }
}
public void Run()
{
_thread.Start(this);
}
public void Stop()
{
_evExit.Set();
}
public void StopAndWait()
{
_evExit.Set();
_thread.Join();
}
}
~Worker()
{
Stop();
}
public Worker(TimeSpan interval)
{
_interval = interval;
}
public TimeSpan Interval
{
get { return _interval; }
}
private void DoWork()
{
/* do your work here */
}
public void Start()
{
var context = new WorkerContext(WorkThreadProc, _interval);
if(Interlocked.CompareExchange<WorkerContext>(ref _workerContext, context, null) == null)
{
context.Run();
}
else
{
context.ExitEvent.Close();
throw new InvalidOperationException("Working alredy.");
}
}
public void Stop()
{
var context = Interlocked.Exchange<WorkerContext>(ref _workerContext, null);
if(context != null)
{
context.Stop();
}
}
private void WorkThreadProc(object p)
{
var context = (WorkerContext)p;
// you can use whatever time-measurement mechanism you want
var sw = new System.Diagnostics.Stopwatch();
int sleep = (int)context.Interval.TotalMilliseconds;
while(true)
{
if(context.ExitEvent.WaitOne(sleep)) break;
sw.Reset();
sw.Start();
DoWork();
sw.Stop();
var time = sw.Elapsed;
if(time < _interval)
sleep = (int)(_interval - time).TotalMilliseconds;
else
sleep = 0;
}
context.ExitEvent.Close();
}
public void Dispose()
{
Stop();
GC.SuppressFinalize(this);
}
}

How about using delegates to method f(), queuing them to a stack, and popping the stack as each delegate completes? You still need the timer, of course.

A simple thread is the easiest way to achieve this. Your still not going to be certain that your called 'precisely' when you want, but it should be close.... Also you can decide if you want to skip calls that should happen or attempt to catch back up... Here is simple helper routine for creating the thread.
public static Thread StartTimer(TimeSpan interval, Func<bool> operation)
{
Thread t = new Thread(new ThreadStart(
delegate()
{
DateTime when = DateTime.Now;
TimeSpan wait = interval;
while (true)
{
Thread.Sleep(wait);
if (!operation())
return;
DateTime dt = DateTime.Now;
when += interval;
while (when < dt)
when += interval;
wait = when - dt;
}
}
));
t.IsBackground = true;
t.Start();
return t;
}

For the benefit of people who land here searching for "re-entrancy": (I know this may be too late for the original question)
If one is not averse to using open source libraries that already provide for such functionality, I have successfully achieved this through an implementation using Quartz.NET
When you create a job and attach a trigger, you can specify what should be done if a previous trigger has not completed executing it's job

C# killing a thread

In my app, I have a thread that runs continuously. By using Thread.Sleep(), the function executes every 10 minutes.
I need to be able to kill this thread when a user clicks a button. I know Thread.Abort() is not reliable. I can use a variable to stop the thread, but since it is sleeping it could be another 10 minutes before the thread kills itself.
Any ideas?

Why don't you use a timer to schedule the task every ten minutes instead. That will run your code on a thread pool thread and thus you will not have to manage this yourself.
For more details see the System.Threading.Timer class.

Instead of Thread.Sleep use a System.Threading.ManualResetEvent. The WaitOne method has a timeout just like Thread.Sleep, your thread will sleep for that interval unless the event is triggered first, and the return value tells you whether the interval elapsed or the event was set.

So here's a sample that users timers to do the work as suggested by Brian. Use start/stop as needed. To cleanup the (Program) object once you are done with it make sure you call Dispose.
Just note that when you call Stop it will prevent the timer from firing again, however you still may have a worker thread in the middle of executing the timer_Elapsed handler, i.e. stopping the timer doesn't stop any currently executing worker thread.
using System;
using System.Timers;
namespace TimerApp
{
class Program : IDisposable
{
private Timer timer;
public Program()
{
this.timer = new Timer();
this.timer.Elapsed += new ElapsedEventHandler(timer_Elapsed);
this.timer.AutoReset = true;
this.timer.Interval = TimeSpan.FromMinutes(10).TotalMilliseconds;
}
void timer_Elapsed(object sender, ElapsedEventArgs e)
{
// TODO...your periodic processing, executed in a worker thread.
}
static void Main(string[] args)
{
// TODO...your app logic.
}
public void Start()
{
this.timer.Start();
}
public void Stop()
{
this.timer.Stop();
}
public void Dispose()
{
this.timer.Dispose();
}
}
}

Building on Ben's answer, here's the pattern to help you out...
using System.Threading;
public class MyWorker {
private ManualResetEvent mResetEvent = new ManualResetEvent(false);
private volatile bool mIsAlive;
private const int mTimeout = 6000000;
public void Start()
{
if (mIsAlive == false)
{
mIsAlive = true;
Thread thread = new Thread(new ThreadStart(RunThread));
thread.Start();
}
}
public void Stop()
{
mIsAlive = false;
mResetEvent.Set();
}
public void RunThread()
{
while(mIsAlive)
{
//Reset the event -we may be restarting the thread.
mResetEvent.Reset();
DoWork();
//The thread will block on this until either the timeout
//expires or the reset event is signaled.
if (mResetEvent.WaitOne(mTimeout))
{
mIsAlive = false; // Exit the loop.
}
}
}
public void DoWork()
{
//...
} }

One possibility is to not have it sleep for ten minutes. Have it sleep for 10 seconds then only do its work on every sixtieth wakeup. Then you only have a latency of ten seconds before it stops.
Aside: This is not necessarily the best solution but it's probably the quickest to implement. As with all possibilities you should do a cost/benefit analysis when selecting which solution is right for you.
If ten seconds is still too much, you can drop it further although keep in mind that dropping it too far will result in a possible performance impact.
You're right that you shouldn't kill threads from outside, it's usually a recipe for disaster if you happen to do it while they have a lock on some resource that's not freed on kill. Threads should always be responsible for their own resources, including their lifetimes.

Synchronizing a timer to prevent overlap

I'm writing a Windows service that runs a variable length activity at intervals (a database scan and update). I need this task to run frequently, but the code to handle isn't safe to run multiple times concurrently.
How can I most simply set up a timer to run the task every 30 seconds while never overlapping executions? (I'm assuming System.Threading.Timer is the correct timer for this job, but could be mistaken).

You could do it with a Timer, but you would need to have some form of locking on your database scan and update. A simple lock to synchronize may be enough to prevent multiple runs from occurring.
That being said, it might be better to start a timer AFTER your operation is complete, and just use it one time, then stop it. Restart it after your next operation. This would give you 30 seconds (or N seconds) between events, with no chance of overlaps, and no locking.
Example :
System.Threading.Timer timer = null;
timer = new System.Threading.Timer((g) =>
{
Console.WriteLine(1); //do whatever
timer.Change(5000, Timeout.Infinite);
}, null, 0, Timeout.Infinite);
Work immediately .....Finish...wait 5 sec....Work immediately .....Finish...wait 5 sec....

I'd use Monitor.TryEnter in your elapsed code:
if (Monitor.TryEnter(lockobj))
{
try
{
// we got the lock, do your work
}
finally
{
Monitor.Exit(lockobj);
}
}
else
{
// another elapsed has the lock
}

I prefer System.Threading.Timer for things like this, because I don't have to go through the event handling mechanism:
Timer UpdateTimer = new Timer(UpdateCallback, null, 30000, 30000);
object updateLock = new object();
void UpdateCallback(object state)
{
if (Monitor.TryEnter(updateLock))
{
try
{
// do stuff here
}
finally
{
Monitor.Exit(updateLock);
}
}
else
{
// previous timer tick took too long.
// so do nothing this time through.
}
}
You can eliminate the need for the lock by making the timer a one-shot and re-starting it after every update:
// Initialize timer as a one-shot
Timer UpdateTimer = new Timer(UpdateCallback, null, 30000, Timeout.Infinite);
void UpdateCallback(object state)
{
// do stuff here
// re-enable the timer
UpdateTimer.Change(30000, Timeout.Infinite);
}

instead of locking (which could cause all of your timed scans to wait and eventually stack up). You could start the scan/update in a thread and then just do a check to see if the thread is still alive.
Thread updateDBThread = new Thread(MyUpdateMethod);
...
private void timer_Elapsed(object sender, ElapsedEventArgs e)
{
if(!updateDBThread.IsAlive)
updateDBThread.Start();
}

Starting from .NET 6 there is a new timer available, the PeriodicTimer. This is a lightweight async-enabled timer, that becomes the perfect tool when overlapping executions should be strictly forbidden. You use this timer by writing an asynchronous method with a loop, and invoking it to start the loop:
private Task _operation;
private CancellationTokenSource _operationCancellation = new();
//...
_operation = StartTimer();
//...
private async Task StartTimer()
{
PeriodicTimer timer = new(TimeSpan.FromSeconds(30));
while (true)
{
await timer.WaitForNextTickAsync(_operationCancellation.Token);
try
{
DoSomething();
}
catch (Exception ex)
{
_logger.LogError(ex);
}
}
}
Instead of using a CancellationTokenSource, you can also stop the loop by disposing the PeriodicTimer. In this case the await timer.WaitForNextTickAsync() will return false.
It is possible that the DoSomething will be invoked subsequently with smaller interval than 30 seconds, but it's impossible that it will be invoked in overlapping fashion, unless you start accidentally two asynchronous loops.
This timer does not support disabling and reenabling it. If you need this functionality you could look at the third-party Nito.AsyncEx.PauseTokenSource component.
In case you are targeting a .NET version earlier than .NET 6, you could look at this question for an alternative: Run async method regularly with specified interval.

You could use the AutoResetEvent as follows:
// Somewhere else in the code
using System;
using System.Threading;
// In the class or whever appropriate
static AutoResetEvent autoEvent = new AutoResetEvent(false);
void MyWorkerThread()
{
while(1)
{
// Wait for work method to signal.
if(autoEvent.WaitOne(30000, false))
{
// Signalled time to quit
return;
}
else
{
// grab a lock
// do the work
// Whatever...
}
}
}
A slightly "smarter" solution is as follow in pseudo-code:
using System;
using System.Diagnostics;
using System.Threading;
// In the class or whever appropriate
static AutoResetEvent autoEvent = new AutoResetEvent(false);
void MyWorkerThread()
{
Stopwatch stopWatch = new Stopwatch();
TimeSpan Second30 = new TimeSpan(0,0,30);
TimeSpan SecondsZero = new TimeSpan(0);
TimeSpan waitTime = Second30 - SecondsZero;
TimeSpan interval;
while(1)
{
// Wait for work method to signal.
if(autoEvent.WaitOne(waitTime, false))
{
// Signalled time to quit
return;
}
else
{
stopWatch.Start();
// grab a lock
// do the work
// Whatever...
stopwatch.stop();
interval = stopwatch.Elapsed;
if (interval < Seconds30)
{
waitTime = Seconds30 - interval;
}
else
{
waitTime = SecondsZero;
}
}
}
}
Either of these has the advantage that you can shutdown the thread, just by signaling the event.
Edit
I should add, that this code makes the assumption that you only have one of these MyWorkerThreads() running, otherwise they would run concurrently.

I've used a mutex when I've wanted single execution:
private void OnMsgTimer(object sender, ElapsedEventArgs args)
{
// mutex creates a single instance in this application
bool wasMutexCreatedNew = false;
using(Mutex onlyOne = new Mutex(true, GetMutexName(), out wasMutexCreatedNew))
{
if (wasMutexCreatedNew)
{
try
{
//<your code here>
}
finally
{
onlyOne.ReleaseMutex();
}
}
}
}
Sorry I'm so late...You will need to provide the mutex name as part of the GetMutexName() method call.