How to populate ParentNode and childNode for the selected node programatically in WinForms TreeViewAdv?

private void button1_Click(object sender, System.EventArgs e)
{
   TreeNodeAdv presentNode = this.treeViewAdv1.SelectedNode;
   if(presentNode == null)
      return;
   TreeNodeAdv newNode = new TreeNodeAdv("NewChild");
   presentNode.Nodes.Add(newNode);
}
private void button2_Click(object sender, System.EventArgs e)
{
   TreeNodeAdv newnode = new TreeNodeAdv("Parentnode");
   this.treeViewAdv1.Nodes.Add(newnode);
}

Private Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
   Dim presentNode As TreeNodeAdv = Me.treeViewAdv1.SelectedNode
   If presentNode Is Nothing Then
      Return
   End If
   Dim newNode As TreeNodeAdv = New TreeNodeAdv("NewChild")
   presentNode.Nodes.Add(newNode)
End Sub
Private Sub button2_Click(ByVal sender As Object, ByVal e As System.EventArgs)
   Dim newnode As TreeNodeAdv = New TreeNodeAdv("Parentnode")
   Me.treeViewAdv1.Nodes.Add(newnode)
End Sub