在asp.net 2.0中，要动态从数据库中取出内容，动态增加结点，其实不难，比如以SQL SERVER 2000的PUBS数据库为例子，要以树型列表方式，取出作者，做为根结点，然后取出每位作者写过什么书，作为子结点，可以这样
1@ Page Language="C#"
1@ Import Namespace="System.Data"
1@ Import Namespace="System.Data.SqlClient"
1@ Import Namespace="System.Configuration"
1<html xmlns=" http://www.w3.org/1999/xhtml ">
2<head runat="server">
3<title>Dynamic Population of the TreeView Control</title>
4<script runat="server">
5
6void Node_Populate(object sender,
7
8System.Web.UI.WebControls.TreeNodeEventArgs e)
9
10{
11
12if(e.Node.ChildNodes.Count == 0)
13
14{
15
16switch( e.Node.Depth )
17
18{
19
20case 0:
21
22FillAuthors(e.Node);
23
24break;
25
26case 1:
27
28FillTitlesForAuthors(e.Node);
29
30break;
31
32}
33
34}
35
36}
37
38
39void FillAuthors(TreeNode node)
40
41{
42
43string connString = System.Configuration.ConfigurationSettings.
44
45ConnectionStrings["NorthwindConnnection"].ConnectionString;
46
47SqlConnection connection = new SqlConnection(connString);
48
49SqlCommand command = new SqlCommand("Select * From
50
51authors",connection);
52
53SqlDataAdapter adapter = new SqlDataAdapter(command);
54
55DataSet authors = new DataSet();
56
57adapter.Fill(authors);
58
59if (authors.Tables.Count > 0)
60
61{
62
63foreach (DataRow row in authors.Tables[0].Rows)
64
65{
66
67TreeNode newNode = new
68
69TreeNode(row["au_fname"].ToString() + " " +
70
71row["au_lname"].ToString(),
72
73row["au_id"].ToString());
74
75newNode.PopulateOnDemand = true;
76
77newNode.SelectAction = TreeNodeSelectAction.Expand;
78
79node.ChildNodes.Add(newNode);
80
81}
82
83}
84
85}
86
87
88void FillTitlesForAuthors(TreeNode node)
89
90{
91
92string authorID = node.Value;
93
94string connString = System.Configuration.ConfigurationSettings.
95
96ConnectionStrings["NorthwindConnnection"].ConnectionString;
97
98SqlConnection connection = new SqlConnection(connString);
99
100SqlCommand command = new SqlCommand("Select T.title,
101
102T.title_id From titles T" +
103
104" Inner Join titleauthor TA on
105
106T.title_id = TA.title_id " +
107
108" Where TA.au_id = '" + authorID + "'", connection);
109
110SqlDataAdapter adapter = new SqlDataAdapter(command);
111
112DataSet titlesForAuthors = new DataSet();
113
114adapter.Fill(titlesForAuthors);
115
116if (titlesForAuthors.Tables.Count > 0)
117
118{
119
120foreach (DataRow row in titlesForAuthors.Tables[0].Rows)
121
122{
123
124TreeNode newNode = new TreeNode(
125
126row["title"].ToString(), row["title_id"].ToString());
127
128newNode.PopulateOnDemand = false;
129
130newNode.SelectAction = TreeNodeSelectAction.None;
131
132node.ChildNodes.Add(newNode);
133
134}
135
136}
137
138}
139
140
141</script>
142</head>
143<body>
144<form id="form1" runat="server">
145<div>
146<asp:treeviewrunat="server" collapseimageurl="Images/open.gif" expandimageurl="Images/closed.gif" id="tvwauthors" ontreenodepopulate="Node_Populate">
147<nodes>
148<asp:treenodetext="authors" populateondemand="true" value="0"></asp:treenodetext="authors">
149</nodes>
150
151</asp:treeviewrunat="server"></div>
152</form>
153</body>
154</html>
其中，注意ontreenodepopulate事件，是在展开树的结点时发生的，这里定义了自定义的NODE_POPULATE,在node_populate中，检查当前结点的深度，如果是0，就是根结点，于是就调用FillAuthors过程，取出所有的作者，如果深度是1，则是叶子结点，调用FillTitlesForAuthors过程。其中，要注意它们中的动态建立树结点的过程，如：
TreeNode newNode = new ** TreeNode ** (row["au_fname"].ToString() + " " +
row["au_lname"].ToString(),
row["au_id"].ToString());
newNode.PopulateOnDemand = true;
newNode.SelectAction = ** TreeNodeSelectAction ** .Expand;
node.ChildNodes.Add(newNode);
其中， popluateondemand属性表明，该结点会动态扩展。