C# treeview复选框选中 父节点选中 相应的子节点也被选中

        #region treeview的复选框选中方法

        /// <summary>
        /// 判断同级的节点是否全选
        /// </summary>
        /// <param name="n">当前选中的节点名称</param>
        /// <returns>是否选中</returns>
        private bool nextCheck(TreeNode n)
        {
            foreach (TreeNode tn in n.Parent.Nodes)
            {
                if (tn.Checked == false)
                    return false;
            }
            return true;
        }

        /// <summary>
        /// 判断同级的节点是否全不选
        /// </summary>
        /// <param name="n">当前选中的节点名称</param>
        /// <returns>是否全不选</returns>
        private bool nextNotCheck(TreeNode n)
        {
            if (n.Checked == true)
            {
                return false;
            }
            if (n.NextNode == null)
            {