asp.net TreeView

  <div style="font-size:14px;">
                        <asp:TreeView ShowCheckBoxes="All" ID="usertree" runat="server" OnTreeNodeCheckChanged="MyTreeView_TreeNodeCheckChanged" OnSelectedNodeChanged="MyTreeView_SelectedNodeChanged" >
                        </asp:TreeView>
                    </div>
    
    
    
               <div style="float:left;">
           <span style="display:block">要参加人员：</span>
            <asp:ListBox ID="NeedExamStaff" AutoPostBack="true" runat="server" Height="262px" Width="116px" SelectionMode="Multiple">
            <asp:ListItem Value="张三"></asp:ListItem>
            <asp:ListItem Value="李四"></asp:ListItem>
            <asp:ListItem>王五</asp:ListItem>
            </asp:ListBox>
                <hr />
             <span style="margin-bottom:0px">总 人 员：<asp:TextBox ID="NeedStaffNumber" runat="server" Text="" Enabled="false" Height="16px" Width="56px"></asp:TextBox><br /><span style="color:red;font-size:small" id="VNeedStaffNumber" runat="server"></span></span>

             </div>  
             <asp:Button ID="Button1" runat="server" Text="确定" OnClick="Button1_Click" Height="21px" />

       DataTable dt = new DataTable();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {

                SqlConnection conn = new SqlConnection();
                conn.ConnectionString = "User ID=sa;Initial Catalog=newtest;Data Source=JJ-PC;Password=123";

                // 打开连接
                if (conn.State == ConnectionState.Closed)
                {
                    conn.Open();
                }

                var sql = "select * from city";

                // 初始化命令
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = conn;
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = sql;

                // 用于执行数据插入、更新和删除的操作；返回被影响的行数。
                int i = cmd.ExecuteNonQuery();



                // 如果想获取数据集合的话我们经常使用到的是数据适配器

                SqlDataAdapter adapter = new SqlDataAdapter();
                adapter.SelectCommand = cmd;
                adapter.Fill(dt);
                this.usertree.Nodes.Clear();
                usertree.Attributes.Add("onclick", " postBackByObject()");

                AddTree(110000, (TreeNode)null);
            }
        }



        //递归添加树的节点
        public void AddTree(int ParentID, TreeNode pNode)
        {
            DataTable ds = dt;
            DataView dvTree = new DataView(ds);
            //过滤ParentID,得到当前的所有子节点
            dvTree.RowFilter = "[fatherID] = " + ParentID;

            foreach (DataRowView Row in dvTree)
            {
                TreeNode Node = new TreeNode();
                if (pNode == null)
                {
                    //添加根节点
                    Node.Text = Row[2].ToString();
                    Node.Value = Row[1].ToString();
                    this.usertree.Nodes.Add(Node);
                    Node.Expanded = true;
                    Node.ShowCheckBox = true;
                    //再次递归
                    AddTree(Int32.Parse(Row[1].ToString()), Node);
                }
                else
                {
                    //添加当前节点的子节点
                    Node.Text = Row[2].ToString();
                    Node.Value = Row[1].ToString();
                    pNode.ChildNodes.Add(Node);
                    Node.Expanded = true;
                    Node.ShowCheckBox = true;
                    //再次递归
                    AddTree(Int32.Parse(Row[1].ToString()), Node);
                }
            }
        }

        protected void MyTreeView_TreeNodeCheckChanged(object sender, TreeNodeEventArgs e)
        {
            TreeNode node = e.Node;
            var nodeCount = node.ChildNodes.Count;
            if (node.Checked == true)
            {
                if (nodeCount > 0)
                {
                    for (var i = 0; i < nodeCount; i++)
                    {
                        node.ChildNodes[i].Checked = true;
                        var node1Count = node.ChildNodes[i].ChildNodes.Count;
                        if (node1Count > 0)
                        {
                            for (var k = 0; k < node1Count; k++)
                            {
                                node.ChildNodes[i].ChildNodes[k].Checked = true;
                                var node2Count = node.ChildNodes[i].ChildNodes[k].ChildNodes.Count;
                                if (node2Count > 0)
                                {
                                    for (var j = 0; j < node2Count; j++)
                                    {
                                        node.ChildNodes[i].ChildNodes[k].ChildNodes[j].Checked = true;
                                    }
                                }
                            }
                        }
                    }
                }
            }
            else
            {
                if (nodeCount > 0)
                {
                    for (var i = 0; i < nodeCount; i++)
                    {
                        node.ChildNodes[i].Checked = false;
                        var node1Count = node.ChildNodes[i].ChildNodes.Count;
                        if (node1Count > 0)
                        {
                            for (var k = 0; k < node1Count; k++)
                            {
                                node.ChildNodes[i].ChildNodes[k].Checked = false;
                                var node2Count = node.ChildNodes[i].ChildNodes[k].ChildNodes.Count;
                                if (node2Count > 0)
                                {
                                    for (var j = 0; j < node2Count; j++)
                                    {
                                        node.ChildNodes[i].ChildNodes[k].ChildNodes[j].Checked = false;
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }

        protected void MyTreeView_SelectedNodeChanged(object sender, EventArgs e)
        {
            var tt = usertree.SelectedNode.Checked;
            var dd = usertree.SelectedValue;
            databind();
        }

        public void databind()
        {

            if (usertree.SelectedNode.Checked == false)
            {
                if (usertree.SelectedNode.ChildNodes.Count > 0)
                {
                    foreach (TreeNode subNode in usertree.SelectedNode.ChildNodes)
                    {
                        usertree.SelectedNode.Checked = true;
                        subNode.Checked = true;
                        if (subNode.ChildNodes.Count > 0)
                        {
                            foreach (TreeNode subNode2 in subNode.ChildNodes)
                            {
                                subNode2.Checked = true;

                                if (subNode2.ChildNodes.Count > 0)
                                {
                                    foreach (TreeNode subNode3 in subNode2.ChildNodes)
                                    {
                                        subNode3.Checked = true;
                                    }
                                }
                            }
                        }
                    }
                }
                else
                {
                    usertree.SelectedNode.Checked = true;
                }
            }
            else
            {
                if (usertree.SelectedNode.ChildNodes.Count > 0)
                {
                    foreach (TreeNode subNode in usertree.SelectedNode.ChildNodes)
                    {
                        usertree.SelectedNode.Checked = false;
                        subNode.Checked = false;
                        if (subNode.ChildNodes.Count > 0)
                        {
                            foreach (TreeNode subNode2 in subNode.ChildNodes)
                            {
                                subNode2.Checked = false;

                                if (subNode2.ChildNodes.Count > 0)
                                {
                                    foreach (TreeNode subNode3 in subNode2.ChildNodes)
                                    {
                                        subNode3.Checked = false;
                                    }
                                }
                            }
                        }
                    }
                }
                else
                {
                    usertree.SelectedNode.Checked = false;
                }
            }
            usertree.SelectedNode.Selected = false;
        }




        protected void Button1_Click(object sender, EventArgs e)
        {
            foreach (TreeNode tn in usertree.CheckedNodes)
            {
                try
                {

                    string userid = tn.Value.ToString();
                  
                        ListItem li = new ListItem();
                       li.Text = tn.Value;
                       li.Value = tn.Text;

                        var tt = 0;
                        for (var i = 0; i < NeedExamStaff.Items.Count; i++)
                        {

                            if (NeedExamStaff.Items[i].Value == li.Value)
                            {
                                tt = 1;
                            }
                        }

                        if (tt == 0)
                        {
                            this.NeedExamStaff.Items.Add(li);

                            if (this.NeedStaffNumber.Text != "")
                            {
                                this.NeedStaffNumber.Text = (Convert.ToInt32(this.NeedStaffNumber.Text) + 1).ToString();
                                this.VNeedStaffNumber.InnerText = "";
                            }
                            else
                            {
                                this.NeedStaffNumber.Text = "1";
                                this.VNeedStaffNumber.InnerText = "";
                            }

                        }

                    }
                
                catch
                {

                }
            }
        }