how to use this semaphore

        List<int> cuis = PersistencyServices.GetListOfAllCui();             
        ResourceLock = new Semaphore(3, 5);


        foreach (var cui in cuis)
        {

            Thread workThread = new Thread(new ParameterizedThreadStart(Worker));

            workThread.Start(cui);

        }

    }
    public static void Worker(object cui)
    {

        ResourceLock.WaitOne();

        Debug.WriteLine(String.Format("Thre开发者_JAVA百科ad for cui {0} in", cui));

        Thread.Sleep(5000);
        ResourceLock.Release();
    }

This code only allows 3 threads to be in the critical region at a time. But the problem is that because the list contains more that 1 million recors I get a OutOfMemoryException. I think this is because even if the semaphor only allows 3 threads to enter the critical region, but 1 million threads are created that wait for the semaphore. How should I change my code to prevent this? Please help

You really don't want a million threads. It isn't clear what you are doing, but it looks like maybe a Parallel.ForEach(...) will do everything you want here, with little work and plenty of sanity.

If you want to enforce only 3 threads:

Parallel.ForEach(cuis, new ParallelOptions { MaxDegreeOfParallelism = 3 },
        Worker);

with:

public static void Worker(int cui)
{
    Debug.WriteLine(String.Format("Thread for cui {0} in", cui));
    Thread.Sleep(5000);
}

If you really want to use the semaphore, use the WaitOne to the loop:

foreach (var cui in cuis)
{
    ResourceLock.WaitOne();
    Thread workThread = new Thread(new ParameterizedThreadStart(Worker));

    workThread.Start(cui);

}
...
public static void Worker(object cui)
{
    Debug.WriteLine(String.Format("Thread for cui {0} in", cui));

    Thread.Sleep(5000);
    ResourceLock.Release();
}