Resuming C# threads

Question

Possible duplicate question: http://stackoverflow.com/questions/142826/is-there-a-way-to-indefinitely-pause-a-thread

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In my code i do the below

Thread mainThread
//...
mainThread.Resume();

void StartThread()
{
    while (!wantQuit)
    {
        db.runEmail();
        mainThread.Suspend();
    }
}

Then i get the exception below because i call resume when it hasnt been suspended.

System.Threading.ThreadStateException

I notice this warning

warning CS0618: 'System.Threading.Thread.Resume()' is obsolete: 'Thread.Resume has been deprecated.  Please use other classes in System.Threading, such as Monitor, Mutex, Event, and Semaphore, to synchronize Threads or protect resources.  http://go.microsoft.com/fwlink/?linkid=14202'

So i wonder is there a way to resume and ignore the exception/case that it is not suspended? I hate writing the below instead of just one line

        try
        {
            mainThread.Resume();
        }
        catch (System.Threading.ThreadStateException e)
        {
        }

Answer 1

You might want to take a look at using a Thread Monitor in this case.

Answer 2

You can check Thread.ThreadState and check for ThreadState.Suspended before resuming.

Answer 3

The easy solution is to fix your logic and don't call Resume() when you are not Suspended().

But the Resume/Suspend API is indeed deprecated, take a look at, for example:

1) Monitor, Wait() and Pulse()

2) AutoResetEvent or ManualResetEvent, Set() and WaitOne()

The static class Monitor is a little easier to use and integrates with lock() {} , but a ResetEvent might be more appropriate here because you can create it in set or unset mode and you are less likely to 'miss' a signal. By contrast, a Monitor.Pulse() will just be lost when the Wait() happens later.

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Will inserted a link in your question, and while I don't consider it a duplicate, the accepted answer there is well suited to cure you from using Suspend/Resume.

Answer 4

WaitHandles are a better approach here.

Instead of suspending your thread, have it wait on a waithandle. When you are ready to start up again, you "set" the handle from the other thread.

For a code example, see MSDN's documentation of ManualResetEvent.