Asp:TreeView 异步加载源码

1.TreeNode的PopulateOnDemand="True"后节点就是动态从后台加载的.
2.但是如果上层TreeView的EnableClientScript="false",就会导致页面Postback
3.TreeView的TreeNodePopulate是PopulateOnDemand="True"并且TreeNode内已有数据才触发的
4.TreeNode的Depth属性是指从根结点算起到现在节点的层数,根结点层数为0
5.TreeNode NewNode = new TreeNode(row["CategoryName"].ToString(),row["CategoryID"].ToString())的第一个参数设置了

TreeNode类的Value 属性值.这个属性值会在发生TreeNodePopulate()事件的TreeNode对像回传用到.sqlQuery.Parameters.Add

("@categoryid", SqlDbType.Int).Value =node.Value;

MSDN资源:
http://msdn.microsoft.com/zh-cn/library/system.web.ui.webcontrols.treeview.aspx
http://msdn.microsoft.com/zh-cn/library/system.web.ui.webcontrols.treenode.aspx

(本文作者:ikmb   MSN:ikmb@163.com)

附代码:

一、HTML

 

<asp:SqlDataSource ID="SqlDataSource1" runat="server"  
            ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString %>"  
            SelectCommand="SELECT [CategoryID], [CategoryName] FROM [Categories]"> 
        </asp:SqlDataSource> 
        <asp:TreeView ID="TreeView1" runat="server" MaxDataBindDepth="2"  
            ontreenodepopulate="TreeView1_TreeNodePopulate" EnableClientScript="true" ExpandDepth="0"> 
            <Nodes> 
                <asp:TreeNode PopulateOnDemand="True" Text="产品列表" Value="产品列表"></asp:TreeNode> 
            </Nodes> 
        </asp:TreeView>

 

 

 

二、C#

 

protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e) 
        { 
            if (e.Node.ChildNodes.Count == 0) 
            { 
                switch (e.Node.Depth) 
                { 
                    case 0: 
                        PopulateCategories(e.Node); 
                        break; 
                    case 1: 
                        PopulateProducts(e.Node); 
                        break; 
                } 
            } 
        } 

        void PopulateCategories(TreeNode node) 
        { 
            SqlCommand sqlQuery = new SqlCommand( 
                "Select CategoryName, CategoryID From Categories"); 
            DataSet resultSet; 
            resultSet = RunQuery(sqlQuery); 
            if (resultSet.Tables.Count > 0) 
            { 
                foreach (DataRow row in resultSet.Tables[0].Rows) 
                { 
                    TreeNode NewNode = new 
                        TreeNode(row["CategoryName"].ToString(), 
                        row["CategoryID"].ToString()); 
                    NewNode.PopulateOnDemand = true; 
                    NewNode.SelectAction = TreeNodeSelectAction.Expand; 
                    node.ChildNodes.Add(NewNode); 
                } 
            } 
        } 

        void PopulateProducts(TreeNode node) 
        { 
            SqlCommand sqlQuery = new SqlCommand(); 
            sqlQuery.CommandText = "Select ProductName From Products " + 
                " Where CategoryID = @categoryid"; 
            sqlQuery.Parameters.Add("@categoryid", SqlDbType.Int).Value = 
                node.Value; 
            DataSet ResultSet = RunQuery(sqlQuery); 
            if (ResultSet.Tables.Count > 0) 
            { 
                foreach (DataRow row in ResultSet.Tables[0].Rows) 
                { 
                    TreeNode NewNode = new 
                        TreeNode(row["ProductName"].ToString()); 
                    NewNode.PopulateOnDemand = false; 
                    NewNode.SelectAction = TreeNodeSelectAction.None; 
                    node.ChildNodes.Add(NewNode); 
                } 
            } 
        } 

        private DataSet RunQuery(SqlCommand sqlQuery) 
        { 
            string connectionString = 
                ConfigurationManager.ConnectionStrings 
                ["NorthwindConnectionString"].ConnectionString; 
            SqlConnection DBConnection = 
                new SqlConnection(connectionString); 
            SqlDataAdapter dbAdapter = new SqlDataAdapter(); 
            dbAdapter.SelectCommand = sqlQuery; 
            sqlQuery.Connection = DBConnection; 
            DataSet resultsDataSet = new DataSet(); 
            try 
            { 
                dbAdapter.Fill(resultsDataSet); 
            } 
            catch 
            { 
                labelStatus.Text = "Unable to connect to SQL Server."; 
            } 
            return resultsDataSet; 
        }

 

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/ikmb/archive/2008/10/16/3084826.aspx