Asp.net TreeView动态加载节点（一）

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:[e-mail])

 

附代码:

一、HTML

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

二、C#

 

1. protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
2.         {
3.             if (e.Node.ChildNodes.Count == 0)
4.             {
5.                 switch (e.Node.Depth)
6.                 {
7.                     case 0:
8.                         PopulateCategories(e.Node);
9.                         break;
10.                     case 1:
11.                         PopulateProducts(e.Node);
12.                         break;
13.                 }
14.             }
15.         }
17.         void PopulateCategories(TreeNode node)
18.         {
19.             SqlCommand sqlQuery = new SqlCommand(
20.                 "Select CategoryName, CategoryID From Categories");
21.             DataSet resultSet;
22.             resultSet = RunQuery(sqlQuery);
23.             if (resultSet.Tables.Count > 0)
24.             {
25.                 foreach (DataRow row in resultSet.Tables[0].Rows)
26.                 {
27.                     TreeNode NewNode = new
28.                         TreeNode(row["CategoryName"].ToString(),
29.                         row["CategoryID"].ToString());
30.                     NewNode.PopulateOnDemand = true;
31.                     NewNode.SelectAction = TreeNodeSelectAction.Expand;
32.                     node.ChildNodes.Add(NewNode);
33.                 }
34.             }
35.         }
37.         void PopulateProducts(TreeNode node)
38.         {
39.             SqlCommand sqlQuery = new SqlCommand();
40.             sqlQuery.CommandText = "Select ProductName From Products " +
41.                 " Where CategoryID = @categoryid";
42.             sqlQuery.Parameters.Add("@categoryid", SqlDbType.Int).Value =
43.                 node.Value;
44.             DataSet ResultSet = RunQuery(sqlQuery);
45.             if (ResultSet.Tables.Count > 0)
46.             {
47.                 foreach (DataRow row in ResultSet.Tables[0].Rows)
48.                 {
49.                     TreeNode NewNode = new
50.                         TreeNode(row["ProductName"].ToString());
51.                     NewNode.PopulateOnDemand = false;
52.                     NewNode.SelectAction = TreeNodeSelectAction.None;
53.                     node.ChildNodes.Add(NewNode);
54.                 }
55.             }
56.         }
58.         private DataSet RunQuery(SqlCommand sqlQuery)
59.         {
60.             string connectionString =
61.                 ConfigurationManager.ConnectionStrings
62.                 ["NorthwindConnectionString"].ConnectionString;
63.             SqlConnection DBConnection =
64.                 new SqlConnection(connectionString);
65.             SqlDataAdapter dbAdapter = new SqlDataAdapter();
66.             dbAdapter.SelectCommand = sqlQuery;
67.             sqlQuery.Connection = DBConnection;
68.             DataSet resultsDataSet = new DataSet();
69.             try
70.             {
71.                 dbAdapter.Fill(resultsDataSet);
72.             }
73.             catch
74.             {
75.                 labelStatus.Text = "Unable to connect to SQL Server.";
76.             }
77.             return resultsDataSet;
78.         }