Is there a general-purpose object pool for .NET?

Question

I have a class that is expensive to construct, in terms of time and memory. I'd like to maintain a pool of these things and dispense them out on demand to multiple threads in the same process.

Is there a general-purpose object pool that is already tested and proven? (I don't want COM+ pooling.)

Answer 1

Pulled straight from MSDN, here's an example of using one of the new concurrent collection types in .NET 4:

The following example demonstrates how to implement an object pool with a System.Collections.Concurrent.ConcurrentBag<T> as its backing store.

public class ObjectPool<T>
{
    private ConcurrentBag<T> _objects;
    private Func<T> _objectGenerator;

    public ObjectPool(Func<T> objectGenerator)
    {
        if (objectGenerator == null)
            throw new ArgumentNullException("objectGenerator");
        _objects = new ConcurrentBag<T>();
        _objectGenerator = objectGenerator;
    }

    public T GetObject()
    {
        T item;
        if (_objects.TryTake(out item))
            return item;
        return _objectGenerator();
    }

    public void PutObject(T item)
    {
        _objects.Add(item);
    }
}