WinForm TreeView 三种状态

private void treeView1_NodeMouseClick(object sender, TreeNodeMouseClickEventArgs e)
        {
            var node = e.Node;
            if (node == null) return;
            //根据父节点状态，全选或全消子节点
            node.StateImageIndex = node.StateImageIndex ==  ?  : ;
            UpdateSubNodeCheckStatus(node);

            //确定子节点的父节点是否被选中（所有子节点选中时，父节点才选中）
            UpdateParentNodeCheckStatus(node);

            //根节点级别选择互斥
            if (node.StateImageIndex != ) return;
            var rootNode = GetRootByNode(node);
            UncheckNextNode(rootNode);
            UncheckPrevNode(rootNode);
        }
        private static TreeNode GetRootByNode(TreeNode node)
        {
            while (true)
            {
                if (node.Level == )
                {
                    return node;
                }
                var parentNode = node.Parent;
                node = parentNode;
            }
        }

        private void UncheckPrevNode(TreeNode node)
        {
            if (node.PrevNode == null) return;
            node.PrevNode.StateImageIndex = ;
            UpdateSubNodeCheckStatus(node.PrevNode);
            UncheckPrevNode(node.PrevNode);
        }

        private void UncheckNextNode(TreeNode node)
        {
            while (true)
            {
                if (node.NextNode == null) return;
                //node.NextNode.Checked = false;
                node.NextNode.StateImageIndex = ;
                UpdateSubNodeCheckStatus(node.NextNode);
                node = node.NextNode;

            }
        }

        private static void UpdateParentNodeCheckStatus(TreeNode node)
        {
            var parentNode = node.Parent;
            if (parentNode == null) return;

            if (IsSubNodeAllCheck(parentNode))
            {
                parentNode.StateImageIndex = ;
            }
            else if (IsSubNodeAllUncheck(parentNode))
            {
                parentNode.StateImageIndex = ;
            }
            else
            {
                parentNode.StateImageIndex = ;
            }

            UpdateParentNodeCheckStatus(parentNode);
        }

        private void UpdateSubNodeCheckStatus(TreeNode parentNode)
        {
            var node = parentNode;
            foreach (TreeNode subNode in node.Nodes)
            {
                subNode.StateImageIndex = node.StateImageIndex;
                UpdateSubNodeCheckStatus(subNode);
            }
        }

        //判断节点的子节点是否全选
        private static bool IsSubNodeAllCheck(TreeNode parentNode)
        {
            return parentNode.Nodes.Cast<TreeNode>().All(subNode => subNode.StateImageIndex==);
        }

        //判断同级的节点是否全不选
        private static bool IsSubNodeAllUncheck(TreeNode parentNode)
        {
            return parentNode.Nodes.Cast<TreeNode>().All(subNode => subNode.StateImageIndex==);
        }