TreeNode.Expand Method ()


Expands the current tree node.

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

public void Expand()

Use the Expand method to conveniently expand the current node.


As an alternative, you can also set the Expanded property to true.

To expand the current node and all its child nodes, consider using the ExpandAll method.

ExpandAll will expand all the nodes in the entire tree.

The value of this property is stored in view state.

The following code example demonstrates how to use the Expand method to programmatically expand a node in the TreeView control. For this example to work correctly, you must copy the sample XML data below to a file named Book.xml.

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

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

  void Data_Bound(Object sender, TreeNodeEventArgs e)

    // Determine the depth of a node as it is bound to data.
    // If the depth is 1, expand the node.
    if(e.Node.Depth == 1)

      // Expand the node using the Expand method.


      // Collapse the node using the Collapse method.




<html xmlns="" >
  <head runat="server">
    <title>TreeNode Expand and Collapse Example</title>
    <form id="form1" runat="server">

      <h3>TreeNode Expand and Collapse Example</h3>

      <h5>Expand the root node. Notice that the child nodes are already expanded.</h5>

      <asp:TreeView id="BookTreeView" 

          <asp:TreeNodeBinding DataMember="Book" TextField="Title"/>
          <asp:TreeNodeBinding DataMember="Chapter" TextField="Heading"/>
          <asp:TreeNodeBinding DataMember="Section" TextField="Heading"/>


      <asp:XmlDataSource id="BookXmlDataSource"  


The following code is sample XML data for the previous example.

<Book Title="Book Title">
    <Chapter Heading="Chapter 1">
        <Section Heading="Section 1">
        <Section Heading="Section 2">
    <Chapter Heading="Chapter 2">
        <Section Heading="Section 1">

.NET Framework
Available since 2.0
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