public void Reverse()
{
    if (_first == null || _first.Next == null)
        return;
    _last = _first;

    var item = _first;
    var next = _first.Next;
    LinkedItem<T> previous = null;

    while (item != null)
    {
        item.Next = previous;
        if (next == null)
            break;

        previous = item;
        item = next;
        next = next.Next;
    }

    _first = item;
}