I'm having the same issue. The Whitepaper has a code example that has the following. But I still can't get it to work correctly. Anyone have some ideas?
Public Sub OnClick(ByVal sender As Object, ByVal e As EventArgs)
' do something with foobar.SelectedNode
End Sub
<asp:TreeView ID="foobar" runat="server" OnSelectedNodeChanged="OnClick" OnAdaptedSelectedNodeChanged="OnClick" />