TreeNode.SelectAction 属性的重要作用

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.NET Framework 类库
TreeNode.SelectAction 属性

在.Net1.1时大家就对treeview控件有很强烈兴趣，但这是个既可爱又可恨的家伙。

当点击树的父亲项目时的展开与收缩，非得点前面的展开符号。

为此很多朋友采用了javascript去改写。以避免产生自动提交的问题

但.Net2.0此功能已经有加强！

增加了属性：TreeNode.SelectAction

选择操作	说明
TreeNodeSelectAction.Expand	切换节点的展开和折叠状态。相应地引发 TreeNodeExpanded 事件或 TreeNodeCollapsed 事件。
TreeNodeSelectAction.None	在选定节点时不引发任何事件。
TreeNodeSelectAction.Select	在选定节点时引发 SelectedNodeChanged 事件。
TreeNodeSelectAction.SelectExpand	选择节点时引发 SelectedNodeChanged 和 TreeNodeExpanded 事件。节点只会展开，不会折叠。

C#

1. <%@ Page Language="C#" %>
   
2. <%@ Import Namespace="System.Data" %>
   
3. <%@ Import Namespace="System.Data.SqlClient" %>
   
4. 
   
5. <script runat="server">
   
6. 
   
7. void PopulateNode(Object sender, TreeNodeEventArgs e)
   
8. {
   
9. 
   
10. // Call the appropriate method to populate a node at a particular level.
    
11. switch(e.Node.Depth)
    
12. {
    
13. case 0:
    
14. // Populate the first-level nodes.
    
15. PopulateCategories(e.Node);
    
16. break;
    
17. case 1:
    
18. // Populate the second-level nodes.
    
19. PopulateProducts(e.Node);
    
20. break;
    
21. default:
    
22. // Do nothing.
    
23. break;
    
24. }
    
25. 
    
26. }
    
27. 
    
28. void PopulateCategories(TreeNode node)
    
29. {
    
30. 
    
31. // Query for the product categories. These are the values
    
32. // for the second-level nodes.
    
33. DataSet ResultSet = RunQuery("Select CategoryID, CategoryName From Categories");
    
34. 
    
35. // Create the second-level nodes.
    
36. if(ResultSet.Tables.Count > 0)
    
37. {
    
38. 
    
39. // Iterate through and create a new node for each row in the query results.
    
40. // Notice that the query results are stored in the table of the DataSet.
    
41. foreach (DataRow row in ResultSet.Tables[0].Rows)
    
42. {
    
43. 
    
44. // Create the new node. Notice that the CategoryId is stored in the Value property
    
45. // of the node. This will make querying for items in a specific category easier when
    
46. // the third-level nodes are created.
    
47. TreeNode newNode = new TreeNode();
    
48. newNode.Text = row["CategoryName"].ToString();
    
49. newNode.Value = row["CategoryID"].ToString();
    
50. 
    
51. // Set the PopulateOnDemand property to true so that the child nodes can be
    
52. // dynamically populated.
    
53. newNode.PopulateOnDemand = true;
    
54. 
    
55. // Set additional properties for the node.
    
56. newNode.SelectAction = TreeNodeSelectAction.Expand;
    
57. 
    
58. // Add the new node to the ChildNodes collection of the parent node.
    
59. node.ChildNodes.Add(newNode);
    
60. 
    
61. }
    
62. 
    
63. }
    
64. 
    
65. }
    
66. 
    
67. void PopulateProducts(TreeNode node)
    
68. {
    
69. 
    
70. // Query for the products of the current category. These are the values
    
71. // for the third-level nodes.
    
72. DataSet ResultSet = RunQuery("Select ProductName From Products Where CategoryID=" + node.Value);
    
73. 
    
74. // Create the third-level nodes.
    
75. if(ResultSet.Tables.Count > 0)
    
76. {
    
77. 
    
78. // Iterate through and create a new node for each row in the query results.
    
79. // Notice that the query results are stored in the table of the DataSet.
    
80. foreach (DataRow row in ResultSet.Tables[0].Rows)
    
81. {
    
82. 
    
83. // Create the new node.
    
84. TreeNode NewNode = new TreeNode(row["roductName"].ToString());
    
85. 
    
86. // Set the PopulateOnDemand property to false, because these are leaf nodes and
    
87. // do not need to be populated.
    
88. NewNode.PopulateOnDemand = false;
    
89. 
    
90. // Set additional properties for the node.
    
91. NewNode.SelectAction = TreeNodeSelectAction.None;
    
92. 
    
93. // Add the new node to the ChildNodes collection of the parent node.
    
94. node.ChildNodes.Add(NewNode);
    
95. 
    
96. }
    
97. 
    
98. }
    
99. 
    
100. }
     
101. 
     
102. DataSet RunQuery(String QueryString)
     
103. {
     
104. 
     
105. // Declare the connection string. This example uses Microsoft SQL Server
     
106. // and connects to the Northwind sample database.
     
107. String ConnectionString = "server=localhost;database=NorthWind;Integrated Security=SSPI";
     
108. 
     
109. SqlConnection DBConnection = new SqlConnection(ConnectionString);
     
110. SqlDataAdapter DBAdapter;
     
111. DataSet ResultsDataSet = new DataSet();
     
112. 
     
113. try
     
114. {
     
115. 
     
116. // Run the query and create a DataSet.
     
117. DBAdapter = new SqlDataAdapter(QueryString, DBConnection);
     
118. DBAdapter.Fill(ResultsDataSet);
     
119. 
     
120. // Close the database connection.
     
121. DBConnection.Close();
     
122. 
     
123. }
     
124. catch(Exception ex)
     
125. {
     
126. 
     
127. // Close the database connection if it is still open.
     
128. if(DBConnection.State == ConnectionState.Open)
     
129. {
     
130. DBConnection.Close();
     
131. }
     
132. 
     
133. Message.Text = "Unable to connect to the database.";
     
134. 
     
135. }
     
136. 
     
137. return ResultsDataSet;
     
138. 
     
139. }
     
140. 
     
141. </script>
     
142. 
     
143. <html>
     
144. <body>
     
145. <form runat="server">
     
146. 
     
147. <h3>TreeView PopulateNodesFromClient Example</h3>
     
148. 
     
149. <asp:TreeView id="LinksTreeView"
     
150. Font-Name= "Arial"
     
151. ForeColor="Blue"
     
152. EnableClientScript="true"
     
153. PopulateNodesFromClient="true"
     
154. OnTreeNodePopulate="opulateNode"
     
155. runat="server">
     
156. 
     
157. <Nodes>
     
158. 
     
159. <asp:TreeNode Text="Inventory"
     
160. SelectAction="Expand"
     
161. PopulateOnDemand="true"/>
     
162. 
     
163. </Nodes>
     
164. 
     
165. </asp:TreeView>
     
166. 
     
167. <br><br>
     
168. 
     
169. <aspabel id="Message" runat="server"/>
     
170. 
     
171. </form>
     
172. </body>
     
173. </html>

复制代码

详细见：http://msdn.microsoft.com/zh-cn/library/system.web.ui.webcontrols.treenode.selectaction(VS.80).aspx