public class Test : IDisposable
{
    private readonly List<IDisposable> _streams = new List<IDisposable>();

    public Test()
    {
        _streams.Add(new MemoryStream());
    }

    public void Dispose()
    {
        foreach (IDisposable disposable in _streams)
        {
            disposable.Dispose();
        }
    }
}