I just ran into a similar scenario (“I am interested in a fast Add and Contains and Remove”) and implemented this sucker:
using System.Collections.Generic;
using System.Threading;
namespace BlahBlah.Utilities
{
public class ConcurrentHashSet<T> : IDisposable
{
private readonly ReaderWriterLockSlim _lock = new ReaderWriterLockSlim(LockRecursionPolicy.SupportsRecursion);
private readonly HashSet<T> _hashSet = new HashSet<T>();
#region Implementation of ICollection<T> ...ish
public bool Add(T item)
{
try
{
_lock.EnterWriteLock();
return _hashSet.Add(item);
}
finally
{
if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
}
}
public void Clear()
{
try
{
_lock.EnterWriteLock();
_hashSet.Clear();
}
finally
{
if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
}
}
public bool Contains(T item)
{
try
{
_lock.EnterReadLock();
return _hashSet.Contains(item);
}
finally
{
if (_lock.IsReadLockHeld) _lock.ExitReadLock();
}
}
public bool Remove(T item)
{
try
{
_lock.EnterWriteLock();
return _hashSet.Remove(item);
}
finally
{
if (_lock.IsWriteLockHeld) _lock.ExitWriteLock();
}
}
public int Count
{
get
{
try
{
_lock.EnterReadLock();
return _hashSet.Count;
}
finally
{
if (_lock.IsReadLockHeld) _lock.ExitReadLock();
}
}
}
#endregion
#region Dispose
public void Dispose()
{
if (_lock != null) _lock.Dispose();
}
#endregion
}
}
Haven’t really tested it (performance- or reliability-wise). YMMV.