private Transform[] allChildrenHelper(List<Transform> children)
{
    foreach (Transform child in Children)
    {
        children.Add(child);
        children = (List<Transform>)children.Concat(allChildrenHelper(children));
    }
    return children.ToArray();
}
/// <summary>
/// Gets all children of this game object.
/// </summary>
public Transform[] AllChildren => allChildrenHelper(new List<Transform>());

private Transform[] allChildrenHelper(List<Transform> children)
{
    foreach (Transform child in Children)
    {
        children.Add(child);
        children = (List<Transform>)children.Concat(allChildrenHelper(children));
    }
    return children.ToArray();
}
/// <summary>
/// Gets all children of this game object.
/// </summary>
public Transform[] AllChildren => allChildrenHelper(new List<Transform>());