C# TreeView --TvHelper

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Windows.Forms;

namespace RF.Sys.Helper
{
    public class TvHelper
    {
        //定义一个用于保存静态变量的实例
        private static TvHelper instance = null;
        //定义一个保证线程同步的标识
        private static readonly object locker = new object();
        //构造函数为私有，使外界不能创建该类的实例
        private TvHelper() { }
        public static TvHelper Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (locker)
                    {
                        if (instance == null) instance = new TvHelper();
                    }
                }
                return instance;
            }
        }

        public void CheckParentNode(TreeNode node)
        {
            if (node.Parent != null)
            {
                if (node.Checked)
                {
                    node.Parent.Checked = node.Checked;
                    CheckParentNode(node.Parent);
                }
                else
                {
                    bool select = false;
                    foreach (TreeNode temp in node.Parent.Nodes)
                    {
                        select = select | temp.Checked;
                    }
                    if (select) node.Parent.Checked = true;
                    else node.Parent.Checked = false;
                    CheckParentNode(node.Parent);
                }
            }
        }

        public void CheckChildNode(TreeNode node)
        {
            if (node.Nodes.Count <= 0) return;

            foreach (TreeNode temp in node.Nodes)
            {
                temp.Checked = node.Checked;
                CheckChildNode(temp);
            }
        }
    }
}

 #region tv event
        private void btnCloseAllNode_Click(object sender, EventArgs e)
        {
            if (btnCloseAllNode.Text == "折叠所有节点")
            {
                this.tvCase.CollapseAll();
                btnCloseAllNode.Text = "展开所有节点";
            }
            else
            {
                this.tvCase.ExpandAll();
                btnCloseAllNode.Text = "折叠所有节点";
            }
        }

        private void btnCloseBandNode_Click(object sender, EventArgs e)
        {
            btnCloseBandNode.Text = "展开所有节点";
            foreach (TreeNode networknode in this.tvCase.Nodes)
            {
                foreach (TreeNode bandnode in networknode.Nodes)
                {
                    bandnode.Collapse();
                }
            }
        }

        private void tvCase_AfterSelect(object sender, TreeViewEventArgs e)
        {
            TreeNode node = (TreeNode)e.Node;
            node.SelectedImageIndex = node.ImageIndex;
        }

        private void tvCase_AfterCheck(object sender, TreeViewEventArgs e)
        {
            TreeNode checknode = e.Node;
            if (e.Action != TreeViewAction.Unknown)
            {
                TvHelper.Instance.CheckChildNode(checknode);
                TvHelper.Instance.CheckParentNode(checknode);
            }
        }

        #endregion