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TreeNodeEventHandler Delegate

Represents the method that will handle the TreeNodeCollapsed, TreeNodeDataBound, TreeNodeExpanded, or TreeNodePopulate event of the TreeView control.

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

public delegate void TreeNodeEventHandler(
	Object sender,
	TreeNodeEventArgs e


Type: System.Object

The source of the event.

Type: System.Web.UI.WebControls.TreeNodeEventArgs

A TreeNodeEventArgs that contains the event data.

When you create a TreeNodeEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see Events and Delegates.

The following code example demonstrates how to use the TreeNodeEventHandler delegate to register an event-handling method programmatically.

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

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

  void Page_Load(Object sender, EventArgs e)

    // Create a new TreeView control.
    TreeView NewTree = new TreeView();

    // Set the properties of the TreeView control.
    NewTree.ID = "BookTreeView";
    NewTree.DataSourceID = "BookXmlDataSource";

    // Create the tree node binding relationship. 

    // Create the root node binding.
    TreeNodeBinding RootBinding = new TreeNodeBinding();
    RootBinding.DataMember = "Book";
    RootBinding.TextField = "Title";

    // Create the parent node binding.
    TreeNodeBinding ParentBinding = new TreeNodeBinding();
    ParentBinding.DataMember = "Chapter";
    ParentBinding.TextField = "Heading";

    // Create the leaf node binding.
    TreeNodeBinding LeafBinding = new TreeNodeBinding();
    LeafBinding.DataMember = "Section";
    LeafBinding.TextField = "Heading";

    // Add bindings to the DataBindings collection.

    // Manually register the event handler for the TreeNodeExpanded event.
    NewTree.TreeNodeExpanded += new TreeNodeEventHandler(this.Node_Expand);

    // Add the TreeView control to the Controls collection of the PlaceHolder control.


  void Node_Expand(Object sender, TreeNodeEventArgs e)

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



<html xmlns="" >
  <head runat="server">
    <title>TreeView TreeNodeEventHandler Example</title>
    <form id="form1" runat="server">

      <h3>TreeView TreeNodeEventHandler Example</h3>

      <asp:PlaceHolder id="ControlPlaceHolder" runat="server">

      <asp:XmlDataSource id="BookXmlDataSource"  

      <br /><br />

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


Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0