Cleaner1.cs

///   T is the type to finalize
///   S contains the native state of T to be cleaned up
/// This separation enforces the pattern where the "native" part stored by a managed type is kept in a State
/// The state could even be used as is in T (kind of a SafeHandle holding several native resources)
public class Cleaner<T, S> 
    where T : class
{
    ...

    private readonly ReferenceQueue<T> _queue;

    public Cleaner(Action<S> onCleanup, Action<Exception> onError)
    {
        _onCleanup = onCleanup;
        _onError = onError;

        _queue = new ReferenceQueue<T>();

        ...

    }

    private Action<S> _onCleanup;
    private Action<Exception> _onError;

    ...

    public void Track(T value, S state)
    {
        var phantomReference = new PhantomObjectFinalizer<T, S>(_queue, value, state);
    }

    ...
}