前台：

<script language="javascript">
        function postBackByObject()
        {
            var element = window.event.srcElement;
            if (element.tagName == "INPUT" && element.type == "checkbox")
            {
                var checkedState = element.checked;
                while (element.tagName != "TABLE")
                element = element.parentElement;

                UnCheck(element);
                element = element.nextSibling;
                if (element == null)
                return;

                var childTables = element.getElementsByTagName("TABLE");
                for (var tableIndex = 0; tableIndex < childTables.length; tableIndex++)
                Check(childTables[tableIndex], checkedState);
            }
        }

        function UnCheck(table)
        {
            if (table == null || table.rows[0].cells.length == 2) // This is the root
                return;
            var parentTable = table.parentElement.previousSibling; 
            Check(parentTable, false);
            UnCheck(parentTable);
        }

        function Check(table, checked)
        {
            var checkboxIndex = table.rows[0].cells.length - 1;    
            var cell = table.rows[0].cells[checkboxIndex];
            var checkboxes = cell.getElementsByTagName("INPUT");
            if (checkboxes.length == 1)
                checkboxes[0].checked = checked;
        }
</script>

后台：

  this._offerCounties.Attributes.Add("onclick", "postBackByObject()");

  public void BindCountriesTreeView()
        {
            _offerCounties.Nodes.Clear();
            List<OfferCountry> allCountries = BLLOffer.GetAllCountries();

            DataTable dtCounties = ConvertHelper.ToDataTable<OfferCountry>(allCountries, "Id", "Name", "ParentId");
            intiTree(_offerCounties.Nodes, "-2", dtCounties);

            List<OfferCountry> offerCountries = BLLOffer.GetOfferCounties(_offerId.Value.ToString());
            setOfferCountries(this._offerCounties.Nodes, offerCountries);
        }

        /// <summary>
        /// Bind the treeview
        /// </summary>
        /// <param name="Nds"></param>
        /// <param name="parentId"></param>
        /// <param name="dataSource"></param>
        private void intiTree(TreeNodeCollection Nds, string parentId, DataTable dataSource)
        {
            DataView dv = new DataView();          
            TreeNode tmpNd;
            string strId;

            dv.Table = dataSource;
            dv.RowFilter = "ParentId='" + parentId + "'";

            foreach (DataRowView objRow in dv)
            {
                tmpNd = new TreeNode();
                strId = objRow["Id"].ToString();
                tmpNd.Value = strId.ToString();
                tmpNd.Text = objRow["Name"].ToString();
                tmpNd.ShowCheckBox = true;
                Nds.Add(tmpNd);
                intiTree(Nds[Nds.Count - 1].ChildNodes, strId, dataSource);
            }
        } 

  /// <summary>
        /// Recursive the tree and get the countries checked.
        /// </summary>
        /// <param name="nodes"></param>
        /// <param name="checkedCountry"></param>
        private void RecursiveTreeView(TreeNodeCollection nodes, ref List<OfferCountry> checkedCountry)
        {
            foreach (TreeNode node in nodes)
            {
                if (node.Checked)
                {
                    if (node.ChildNodes.Count == 0)
                    {
                        OfferCountry offerCountry = new OfferCountry();
                        offerCountry.Id = node.Value.ToString();
                        offerCountry.OfferId = _offerId.Value.ToString();
                        checkedCountry.Add(offerCountry);
                    }
                }
                RecursiveTreeView(node.ChildNodes, ref checkedCountry);
            }
        }