multithreading while blocking main thread

multithreading while blocking main thread

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10 years, 6 months ago

10 years, 6 months ago

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How do I start 2 or more threads all at once and block the main thread until the others threads are complete?

c# multithreading

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edited Sep 15 ’09 at 14:35


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asked Sep 15 ’09 at 14:30


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Threading in C# for the question above

– user125155
Sep 15 ’09 at 14:34

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4 Answers





From the main thread, call Thread.Join on each of the other threads.

(EDIT: Now you’ve specified C#, there’s no need for the platform agnostic comment.)

For example:

Thread t1 = new Thread(FirstMethod).Start();
Thread t2 = new Thread(SecondMethod).Start();


It doesn’t matter what order you call Join in, if you only want to wait until they’ve all finished. (If you want to continue when any of them have finished, you need to get into the realm of wait handles.)

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edited Sep 15 ’09 at 14:49

answered Sep 15 ’09 at 14:31

Jon SkeetJon Skeet

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In .NET 4.0 you may also get value out of using a System.Threading.CountdownEvent and calling ‘Signal’ on the child threads and ‘Wait’ on the main thread, or System.Threading.Barrier and call SignalAndWait on all three threads.

– Rick
Sep 16 ’09 at 6:11

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public delegate void AsyncTask(object state);

public void Method1(object state) …..

public void Method2(object state) …..

public void RunAsyncAndWait(){

AsyncTask ac1 = new AsyncTask(Method1);
AsyncTask ac2 = new AsyncTask(Method2);

WaitHandle[] waits = new WaitHandle[2];

IAsyncResult r1 = ac1.BeginInvoke( someData , null , null );
IAsyncResult r2 = ac2.BeginInvoke( someData , null , null );

waits[0] = r1.AsyncWaitHandle;
waits[1] = r2.AsyncWaitHandle;



This works, some people will aruge that if any of thread finishes first it will wait endlessly but I have tried, it have worked always. You can also give timeout to wait for. And in BeginInvoke first parameter is the value passed inside your methods.

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answered Sep 15 ’09 at 14:55

Akash KavaAkash Kava

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There’s a good example of how to do threading in C# on MSDN

If you look at the Mutex example it demonstrates putting the main thread to sleep until all child threads have completed.

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answered Sep 15 ’09 at 14:42


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or Mutex example even 😉

– Gwaredd
Sep 15 ’09 at 14:43

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Jeffry Richter of Wintellect has a library for download called the Power Threading library. I have not used it myself but it might be helpful.

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answered Sep 15 ’09 at 15:02


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