TreeView.TreeNodeExpanded Event


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Occurs when a node is expanded in the TreeView control.

Namespace:   System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

public event TreeNodeEventHandler TreeNodeExpanded

The TreeNodeExpanded event is raised when a node is expanded in the TreeView control. This allows you to provide an event-handling method that performs a custom routine whenever this event occurs.


If the SelectAction property for a node is set to TreeNodeSelectAction.Expand or TreeNodeSelectAction.SelectExpand, the TreeNodeExpanded event is also raised when that node is clicked in the TreeView control.

For more information about handling events, see NIB: Consuming Events.

The following code example demonstrates how to use the TreeNodeExpanded event to update the content of a Label control when the user expands a node in the TreeView control.

<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<script runat="server">

  void Node_Expand(Object sender, TreeNodeEventArgs e)

    Message.Text = "You expanded the " + e.Node.Text + " node.";


  void Node_Collapse(Object sender, TreeNodeEventArgs e)

    Message.Text = "You collapsed the " + e.Node.Text + " node.";



<html xmlns="" >

  <head runat="server">
    <title>TreeView TreeNodeExpand and TreeNodeCollapse Example</title>
    <form id="form1" runat="server">

      <h3>TreeView TreeNodeExpand and TreeNodeCollapse Example</h3>

      <asp:TreeView id="BookTreeView"


          <asp:TreeNode Value="Chapter 1" 
            Text="Chapter 1">

            <asp:TreeNode Value="Section 1"
              Text="Section 1">

              <asp:TreeNode Value="Paragraph 1" 
                Text="Paragraph 1">


            <asp:TreeNode Value="Section 2" 
              Text="Section 2">




      <br />

      <asp:Label id="Message" runat="server"/>


.NET Framework
Available since 2.0
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