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);     } } 

Answer 2

The ObjectPool class proposed by 280Z28 looks pretty good. You might also consider creating another class that implements IDisposable and wraps the return value of GetObject(). This will ensure objects are returned to your pool and reads nicely:

class ObjectPoolReference<T> : IDisposable {     public ObjectPool<T> Pool { get; private set; }      public T Instance { get; private set; }      public ObjectPoolReference(ObjectPool<T> pool, T instance)     {         Pool = pool;         Instance = instance;     }      ~ObjectPoolReference()     {         Dispose();     }      #region IDisposable Members      private bool _Disposed = false;      public void Dispose()     {         if (!_Disposed)         {             Pool.PutObject(Instance);              _Disposed = true;         }     }      #endregion }  //instance of the pool ObjectPool<Foo> Pool;  //"using" ensures the reference is disposed at the end of the block, releasing the object back to the pool using (var Ref = Pool.GetObject()) {     Ref.Instance.DoSomething(); }