Protogame.TreeView.AddChild C# (CSharp) 메소드

        public void AddChild(TreeItem item)
        {
            if (item == null)
            {
                throw new ArgumentNullException(nameof(item));
            }

            if (item.Parent != null)
            {
                throw new InvalidOperationException();
            }

            _items.Add(item);
            item.Parent = this;
        }