[2.0] Binding after postback

[Maury]

Hello,
I have a AccessDataSource (with a Session parameter)
a DetailsView and a Treeview,
when I click on the Treeview I would like to
refresh the DataSource and show the right record...
but it seems that no DataBinding happens...help, thanks!

protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
{
switch (e.Node.Depth)
{
case 0:
[..................]
case 4:
_id = Int32.Parse(e.Node.Value);
SaveState();
DetailsView1.DataSourceID = "AccessDataSource1";
}
}