public void AddChild(IBProjectElement child)
        {
            if (child.Parent != null)
            {
                throw new Exception("IBProjectElement.Parent プロパティが null でありません");
            }

            Children.Add(child);
            child.Parent = this;

            DELETE = false;
        }
 public void RemoveChild(IBProjectElement child)
 {
     Children.Remove(child);
     child.Parent = null;
 }