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TreeNode.Expand Method

Expands the tree node.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public void Expand()

The Expand method expands the current TreeNode down to the next level of nodes.


The state of a TreeNode is persisted. For example, if the next level of child nodes was not collapsed previously, when the Expand method is called, the child nodes appear in their previously expanded state.

The following code example toggles the selected node when a button is clicked. If the selected node is collapsed, it is expanded, if it is expanded by calling the Expand method, it is collapsed by calling the Collapse method. This example requires that you have a Form with a TreeView control that has at least one TreeNode with at least one child TreeNode.

private void button1_Click(object sender, System.EventArgs e)
   if (treeView1.SelectedNode.IsExpanded)
      MessageBox.Show(treeView1.SelectedNode.Text + 
        " tree node collapsed.");
      MessageBox.Show(treeView1.SelectedNode.Text + 
        " tree node expanded.");

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, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

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, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0