public void ClearPhotoStream()
        {
            App.PhotoStreamHelper.RemoveAll();

            _currentMosaicViewModel = null;

            if (_pictures != null)
            {
                _pictures.Dispose();
                _pictures = null;
            }

            if (_enumerator != null)
            {
                _enumerator.Dispose();
                _enumerator = null;
            }

            try
            {
                ListBoxItems.Clear();
            }
            catch (Exception ex)
            {
            }

            GC.Collect();
        }