AutoResetEvent and several sets

Question

I am trying to create a data structure around a stack that locks until the stack has an available item. I tried using AutoResetEvent, but I think I misunderstood how this synchronization process works. Basically, looking at the following code, I try to pop out of the stack when nothing is available.

It seems to AutoResetEventbehave like a semaphore. It's right? Can I just get rid of Set()in BlockingStack.Get()and do with it? Or this will lead to a situation where I use only one of my stack elements.

public class BlockingStack
{
    private Stack<MyType> _internalStack;
    private AutoResetEvent _blockUntilAvailable;

    public BlockingStack()
    {
        _internalStack = new Stack<MyType>(5);
        _blockUntilAvailable = new AutoResetEvent(false);

        for (int i = 0; i < 5; ++i)
        {
            var obj = new MyType();
            Add(obj);
        }
    }

    public MyType Get()
    {
        _blockUntilAvailable.WatiOne();

        lock (_internalStack)
        {
            var obj = _internalStack.Pop();
            if (_internalStack.Count > 0)
            {
                _blockUntilAvailable.Set(); // do I need to do this?
            }

            return obj;
        }
    }

    public void Add(MyType obj)
    {
        lock (_internalStack)
        {
            _internalStack.Push(obj);
            _blockUntilAvailable.Set();
        }
    }
}

AutoResetEvent WaitOne(). , , . -.

EDIT: Silverlight.

Answer 1

Monitor, , :

public class Semaphore
{
    private int _count;
    private int _maximum;
    private object _countGuard;

    public Semaphore(int maximum)
    {
        _count = 0;
        _maximum = maximum;
        _countGuard = new object();
    }

    public void WaitOne()
    {
        while (true)
        {
            lock (_countGuard)
            {
                if (_count < _maximum)
                {
                    _count++;
                    return;
                }
            }
            Thread.Sleep(50);
        }
    }

    public void ReleaseOne()
    {
        lock (_countGuard)
        {
            if (_count > 0)
            {
                _count--;
            }
        }
    }
}

public class BlockingStack
{
    private Stack<MyType> _internalStack;
    private Semaphore _blockUntilAvailable;

    public BlockingStack()
    {
        _internalStack = new Stack<MyType>(5);
        _blockUntilAvailable = new Semaphore(5);

        for (int i = 0; i < 5; ++i)
        {
            var obj = new MyType();
            Add(obj);
        }
    }

    public MyType Get()
    {
        _blockUntilAvailable.WaitOne();

        lock (_internalStack)
        {
            var obj = _internalStack.Pop();
            return obj;
        }
    }

    public void Add(MyType obj)
    {
        lock (_internalStack)
        {
            _internalStack.Push(obj);
            _blockUntilAvailable.ReleaseOne();
        }
    }
}

Answer 2

, , . , :

ConcurrentStack<SomeType> MyStack = new ConcurrentStack<SomeType>();
BlockingCollection<SomeType> SharedStack = new BlockingCollection<SomeType>(MyStack)

, . .

sharedStack, sharedStack.Take(), , - .

---

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Answer 3

, . , Get ( .WaitOne).

, , - :

public class BlockingStack<T>
{
    private Stack<T> _internalStack;
    private AutoResetEvent _blockUntilAvailable;

    public BlockingStack()
    {
        _internalStack = new Stack<T>(5);
        _blockUntilAvailable = new AutoResetEvent(false);
    }

    public T Pop()
    {
        lock (_internalStack)
        {
            if (_internalStack.Count == 0)
                _blockUntilAvailable.WaitOne();

            return _internalStack.Pop();
        }
    }

    public void Push(T obj)
    {
        lock (_internalStack)
        {
            _internalStack.Push(obj);

            if(_internalStack.Count == 0)
                _blockUntilAvailable.Set();
        }
    }
}

, _internalStack 0, Push. , .

---

: 2 :

• Pop .WaitOne, _internalStack, Push .

• Pop , AutoResetEvent - ex. AutoResetEvent, . , , Stack. Stack , , .WaitOne AutoResetEvent, Push , true, .

:

public class BlockingStack<T>
{
    private Stack<T> _internalStack;

    public BlockingStack()
    {
        _internalStack = new Stack<T>(5);
    }

    public T Pop()
    {
        lock (_internalStack)
        {
            if (_internalStack.Count == 0)
                Monitor.Wait(_internalStack);

            return _internalStack.Pop();
        }
    }

    public void Push(T obj)
    {
        lock (_internalStack)
        {
            _internalStack.Push(obj);
            Monitor.Pulse(_internalStack);
        }
    }
}