数据库（数据库名为test）中表的内容：

if exists (select * from sysobjects where id = OBJECT_ID('[ItemTree]') and OBJECTPROPERTY(id, 'IsUserTable') = 1) 
DROP TABLE [ItemTree]

CREATE TABLE [ItemTree] (
[id] [bigint]  IDENTITY (1, 1)  NOT NULL,
[title] [nvarchar]  (50) NOT NULL,
[pageName] [nvarchar]  (50) NULL,
[parentID] [bigint]  NOT NULL)

ALTER TABLE [ItemTree] WITH NOCHECK ADD  CONSTRAINT [PK_ItemTree] PRIMARY KEY  NONCLUSTERED ( [id] )
SET IDENTITY_INSERT [ItemTree] ON

INSERT [ItemTree] ([id],[title],[parentID]) VALUES ( 1,N'会员管理',0)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 2,N'添加会员',N'addmember',1)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 3,N'编辑会员',N'editmember',1)
INSERT [ItemTree] ([id],[title],[parentID]) VALUES ( 4,N'公告管理',0)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 5,N'添加公告',N'addnotice',4)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 6,N'编辑公告',N'editnotice',4)
INSERT [ItemTree] ([id],[title],[parentID]) VALUES ( 7,N'产品管理',0)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 8,N'产品入库',N'inproduct',7)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 9,N'产品出库',N'outproduct',7)
INSERT [ItemTree] ([id],[title],[parentID]) VALUES ( 10,N'产品清单',7)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 12,N'出库清单',N'outproductmenu',10)
INSERT [ItemTree] ([id],[title],[pageName],[parentID]) VALUES ( 13,N'入库清单',N'inproductmenu',10)

SET IDENTITY_INSERT [ItemTree] OFF
if exists (select * from sysobjects where id = OBJECT_ID('[ItemTreeToUsers]') and OBJECTPROPERTY(id, 'IsUserTable') = 1) 
DROP TABLE [ItemTreeToUsers]

CREATE TABLE [ItemTreeToUsers] (
[id] [bigint]  IDENTITY (1, 1)  NOT NULL,
[ItemTreeID] [bigint]  NOT NULL,
[UserID] [bigint]  NOT NULL)

ALTER TABLE [ItemTreeToUsers] WITH NOCHECK ADD  CONSTRAINT [PK_ItemTreeToUsers] PRIMARY KEY  NONCLUSTERED ( [id] )
SET IDENTITY_INSERT [ItemTreeToUsers] ON

INSERT [ItemTreeToUsers] ([id],[ItemTreeID],[UserID]) VALUES ( 1,1,1)
INSERT [ItemTreeToUsers] ([id],[ItemTreeID],[UserID]) VALUES ( 4,7,1)
INSERT [ItemTreeToUsers] ([id],[ItemTreeID],[UserID]) VALUES ( 8,12,1)
INSERT [ItemTreeToUsers] ([id],[ItemTreeID],[UserID]) VALUES ( 9,4,1)
INSERT [ItemTreeToUsers] ([id],[ItemTreeID],[UserID]) VALUES ( 10,2,1)
INSERT [ItemTreeToUsers] ([id],[ItemTreeID],[UserID]) VALUES ( 11,10,1)
INSERT [ItemTreeToUsers] ([id],[ItemTreeID],[UserID]) VALUES ( 12,5,1)

SET IDENTITY_INSERT [ItemTreeToUsers] OFF

数据模型：

界面设计：

操作类：

    public class CommonFuncs
    {
        #region 加载树结构
        /// <summary>
        /// 加载树结构，没有加载权限
        /// </summary>
        /// <param name="tv"></param>
        /// <returns></returns>
        public static TreeView GetTree(TreeView tv)
        {
            DataTable dt = null;
            dt = new Tools.Common.DbHelper().ExecuteDataTable("select * from ItemTree");//获取全部数据到dt中
            var roots = from node in dt.AsEnumerable()
                        where node.Field<long>("parentID") == 0
                        select node;
            tv.Nodes.Clear();
            TreeNode tnode;
            foreach (var node in roots)
            {
                tnode = new TreeNode();
                tnode.Tag = node.Field<long>("parentID");
                tnode.Text = node.Field<string>("title");
                tnode.ToolTipText = node.Field<string>("pageName");
                tnode.Name = node.Field<long>("id").ToString();//Name可用来存放ID，它是唯一的
                tv.Nodes.Add(tnode);
                GetChildNodes(tnode, dt);
            }
            return tv;
        }
        /// <summary>
        /// 加载子节点
        /// </summary>
        /// <param name="parentNode">父节点</param>
        /// <param name="dt">整个结构的dt</param>
        private static void GetChildNodes(TreeNode parentNode, DataTable dt)
        {
            long ID = Convert.ToInt64(parentNode.Name);
            var ChildNodes = from node in dt.AsEnumerable()
                             where node.Field<long>("parentID") == ID
                             select node;
            TreeNode tnode;
            foreach (var node in ChildNodes)
            {
                tnode = new TreeNode();
                tnode.Tag = node.Field<long>("parentID");
                tnode.Text = node.Field<string>("title");
                tnode.ToolTipText = node.Field<string>("pageName");
                tnode.Name = node.Field<long>("id").ToString();
                parentNode.Nodes.Add(tnode);
                if (dt.AsEnumerable().Count(item => item.Field<long>("parentID") == node.Field<long>("id")) > 0)
                {
                    GetChildNodes(tnode, dt);
                }
            }
        }
        #endregion

        #region 加载初始权限到TreeView
        /// <summary>
        /// 加载初始权限到TreeView
        /// </summary>
        /// <param name="tv">TreeView</param>
        /// <param name="userid">用户id号</param>
        public static void GetPermis(TreeView tv, long userid)
        {
            //查询此用户的所有权限
            DataTable dtuserpermission = new Tools.Common.DbHelper().ExecuteDataTable("select * from ItemTreeToUsers where userid=" + userid);
            GetPermission(tv.Nodes, dtuserpermission, userid);
        }
        /// <summary>
        /// 为节点集合初始化选择状态
        /// </summary>
        /// <param name="tns">节点集合</param>
        /// <param name="dt">权限DataTable</param>
        /// <param name="userid">用户id</param>
        private static void GetPermission(TreeNodeCollection tns, DataTable dt, long userid)
        {
            for (int i = 0; i < tns.Count; i++)
            {
                TreeNode tn = tns[i];
                var count = dt.AsEnumerable().Count(item => item.Field<long>("userid") == userid && item.Field<long>("itemtreeID") == Convert.ToInt64(tn.Name));
                if (count == 0)
                {
                    tn.Checked = false;
                }
                else tn.Checked = true;
                if (tn.Nodes.Count > 0)//加载子节点权限
                {
                    GetPermission(tn.Nodes, dt, userid);
                }
            }
        }


        #endregion

        #region 设置TreeView上选择的权限到数据库
        /// <summary>
        /// 设置TreeView上选择的权限到数据库
        /// </summary>
        /// <param name="tv">TreeView</param>
        /// <param name="userid">用户id号</param>
        /// <returns></returns>
        public static bool SetPermis(TreeView tv, long userid)
        {
            bool isSuccess = true;
            try
            {
                TestEntities myEntities = new TestEntities();//TestModel.edmx文件生成的，test为数据库名
                SetPermission(myEntities, tv.Nodes, userid);//这个函数只是标记，并不操作数据库
                myEntities.SaveChanges();//接受更改，一次性写回数据库
            }
            catch
            {
                isSuccess = false;
            }
            return isSuccess;
        }
        /// <summary>
        /// 设置每个节点上的权限到数据库
        /// </summary>
        /// <param name="myEntities"></param>
        /// <param name="tns"></param>
        /// <param name="userid"></param>
        private static void SetPermission(TestEntities myEntities, TreeNodeCollection tns, long userid)
        {
            for (int i = 0; i < tns.Count; i++)
            {

                TreeNode tn = tns[i];
                long id = Convert.ToInt64(tn.Name);
                var OldData = from t in myEntities.ItemTreeToUsers
                              where t.ItemTreeID == id && t.UserID == userid
                              select t;
                if (tn.Checked)
                {
                    if (OldData.Count() == 0)//没有记录才插入
                    {
                        ItemTreeToUsers newUserItem = new ItemTreeToUsers
                        {
                            ItemTreeID = Convert.ToInt64(tn.Name),
                            UserID = userid
                        };
                        myEntities.AddToItemTreeToUsers(newUserItem);
                    }
                }
                else
                {
                    if (OldData.Count() > 0)//有记录才删除
                    {
                        foreach (var toDelete in OldData)//可能的都删除
                        {
                            myEntities.DeleteObject(toDelete);
                        }
                    }
                }

                if (tn.Nodes.Count > 0)//设置子节点权限
                {
                    SetPermission(myEntities, tn.Nodes, userid);
                }
            }
        } 
        #endregion

    }

Form1.cs代码

    public partial class Form1 : Form
    {
        private long UserID = 1;
        private bool isInited=false;
        //构造函数，窗体上 TreeView名称为：TVUser
        public Form1()
        {
            InitializeComponent();
            TVUser.CheckBoxes = true;//TreeView前有复选框
        }
        //初始化
        private void Form1_Load(object sender, EventArgs e)
        {
            loadData();
        }
        //刷新按钮
        private void buttonRefresh_Click(object sender, EventArgs e)
        {
            loadData();
        }
        private void loadData()
        {
            CommonFuncs.GetTree(TVUser);
            CommonFuncs.GetPermis(TVUser, UserID);
            isInited = true;
        }
        //保存按钮
        private void buttonSave_Click(object sender, EventArgs e)
        {
           bool flag= CommonFuncs.SetPermis(TVUser, UserID);
           if (flag)
           {
               MessageBox.Show("设置成功！");
           }
           else
           {
               MessageBox.Show("设置失败！");
           }
        }
        //treeView事件
        private void TVUser_AfterCheck(object sender, TreeViewEventArgs e)
        {
            try
            {
                if (!isInited) return;
                if (e.Node.Checked)
                {
                    if (e.Node.Parent != null)
                    {
                        e.Node.Parent.Checked = true;//选择时，把父节点选中
                    }
                }
                else
                {
                    UnCheckSubNodes(e.Node);
                }
            }
            catch (Exception er)
            {
                MessageBox.Show(er.ToString());
            }
        }

        #region 子节点取消选中
        /// <summary>
        /// 子节点取消选中
        /// </summary>
        /// <param name="node"></param>
        private void UnCheckSubNodes(TreeNode node)
        {
            if (node.Nodes.Count > 0)
            {
                foreach (TreeNode subnode in node.Nodes)
                {
                    subnode.Checked = false;//取消时，把子节点全部取消
                    if (subnode.Nodes.Count > 0)
                    {
                        UnCheckSubNodes(subnode);//无限级取消子节点
                    }
                }
            }
        } 
        #endregion

    }

运行正确，并能将数据更改到数据库。

界面如下：