Visual Basic TreeView Example

FrmKitchenSink.vb

Private Sub TvFileNav_BeforeCollapse(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewCancelEventArgs) Handles TvFileNav.BeforeCollapse
    e.Node.Nodes.Clear()
    e.Node.Nodes.Add("")
End Sub

Private Sub TvFileNav_BeforeExpand(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewCancelEventArgs) Handles TvFileNav.BeforeExpand
    ' clear the expanding node so we can re-populate it, or else we end up with duplicate nodes
    e.Node.Nodes.Clear()

    ' Get the directory representing this node
    Dim dir As IO.DirectoryInfo = New IO.DirectoryInfo(e.Node.Tag.ToString)

    ' Add each subdirectory from the file system to the expanding node as a child node
    For Each subdir As IO.DirectoryInfo In dir.GetDirectories
        ' Declare a child TreeNode for the next subdirectory
        Dim dirNode As New TreeNode

        ' Store the full path to this directory in the child TreeNode's Tag property
        dirNode.Tag = subdir.FullName

        ' Set the child TreeNodes's display text
        dirNode.Text = subdir.Name

        ' Add a dummy TreeNode to this child TreeNode to make it expandable
        dirNode.Nodes.Add("")

        ' Add this child TreeNode to the expanding TreeNode
        e.Node.Nodes.Add(dirNode)
    Next
End Sub