/// <summary>
/// Cuts all the single-child root, returning the first child that has more than 1 child of its own.
/// If the first node has 0 childs, returns itself.
/// Doesn't set the new root node parent to null.
/// </summary>
public ObservableCollection <ModelTreeItem> Trim()
{
if (this.ChildItems.Count == 1)
{
return(ChildItems[0].Trim());
}
else if (!ChildItems.Any(ci => ci.HasData))
{
return(new ObservableCollection <ModelTreeItem>(ChildItems.SelectMany(ci => ci.Trim())));
}
return(new ObservableCollection <ModelTreeItem>(new ModelTreeItem[] { this }));
}