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aspx.cs

    // 向TreeView中动态添加节点
    public void PopulateNode(Object sender, TreeNodeEventArgs e)
    {
        //根据点击的节点深度添加节点
        switch (e.Node.Depth)
        {
            case 0:
                //点击根节点，添加第一级子节点
                PopulateCategories(e.Node);
                break;
            case 1:
                //点击第一级节点，添加第二级子节点
                PopulateProducts(e.Node);
                break;
            default:               
                break;
        }
    }

    ///

    /// 添加第一级子节点
    ///

    ///     private void PopulateCategories(TreeNode node)
    {
        DataSet ResultSet = RunQuery("Select CategoryID, CategoryName From Categories");

        //建立第一级子节点
        if (ResultSet.Tables.Count > 0)
        {
            //将DataSet每一行结果循环添加到父节点下
            foreach (DataRow row in ResultSet.Tables[0].Rows)
            {
                //创建新节点，CategoryId为节点的value属性值
                TreeNode NewNode = new TreeNode(row["CategoryName"].ToString(), row["CategoryID"].ToString());

                //将PopulateOnDemand属性设置为true，可以在此节点下继续添加节点
                NewNode.PopulateOnDemand = true;

                //选中节点时引发TreeNodeExpanded事件
                NewNode.SelectAction = TreeNodeSelectAction.Expand;
                //TreeNodeSelectAction.None; TreeNodeSelectAction.Select; TreeNodeSelectAction.SelectExpand;

                //添加节点
                node.ChildNodes.Add(NewNode);
            }
        }
    }

    ///

    /// 添加第二级子节点
    ///

    ///     private void PopulateProducts(TreeNode node)
    {
        DataSet ResultSet = RunQuery("Select ProductName From Products Where CategoryID=" + node.Value);

        // 建立第二级子节点
        if (ResultSet.Tables.Count > 0)
        {
            //将DataSet每一行结果循环添加到第一级子节点下
            foreach (DataRow row in ResultSet.Tables[0].Rows)
            {

                //创建新节点，节点的value未赋值，若还有第三级子节点，则必须赋值
                TreeNode NewNode = new TreeNode(row["ProductName"].ToString());

                //将PopulateOnDemand属性设置为false，则可以在此节点下继续添加节点，若需要继续添加，需设为true
                NewNode.PopulateOnDemand = false;

                //选中节点不引发任何事件
                NewNode.SelectAction = TreeNodeSelectAction.None;

                // Add the new node to the ChildNodes collection of the parent node.
                node.ChildNodes.Add(NewNode);
            }
        }
    }

    ///

    /// 查询
    ///

    ///     ///
    private DataSet RunQuery(String QueryString)
    {
        String ConnectionString = "server = .; database = Northwind; uid = sa; pwd = 123456Aa;";
       
        SqlConnection DBConnection = new SqlConnection(ConnectionString);
        SqlDataAdapter DBAdapter;
        DataSet ResultsDataSet = new DataSet();

        try
        {
            DBAdapter = new SqlDataAdapter(QueryString, DBConnection);
            DBAdapter.Fill(ResultsDataSet);

            DBConnection.Close();
        }
        catch (Exception ex)
        {
            if (DBConnection.State == ConnectionState.Open)
            {
                DBConnection.Close();
            }
        }

        return ResultsDataSet;
    }