problem with treeview-object...

I had the following problem with a treeview object:

As I have a quite big treeview-object, so that I store the built treeview-object in a session-variable (to win time when reloading a page). But when I attributed the stored object to the object placed in the page, the tree stays blanc. (first code)

To resolve the problem I put a placeholder in the page and then I attributed to the placeholder the treeview-object (second code). But now I do not know how to handle when someone clicks a noed-item.

So my problem can have two solutions:
1) get rid of the place-holder-solution and find how to attribute the stored treeview object to the treeview-object that is in the page. (=> I would prefer this solution)
2) or find out how to manage click events on the tree-object, when it is stored in a place-holder.

I would be very thankful if anybody could help me !!



first code (without placehoder, but it doesn't work when loading the page)

VB Code:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        fill_TreeView()
    End Sub
    Public my_hierarchy As hierarchy
    Public my_dataset As DataSet
    Protected WithEvents TreeView1 As Microsoft.Web.UI.WebControls.TreeView
    Sub New()
        my_hierarchy = HttpContext.Current.Session("my_product_hierarchy")
        my_dataset = my_hierarchy.my_dataset_all_hierarchy_elements
    End Sub
    Public Function fill_TreeView()
        If HttpContext.Current.Session("my_TreeView") Is Nothing Then
            Treeview1 = New Microsoft.Web.UI.WebControls.TreeView
            Dim TreeNode As Microsoft.Web.UI.WebControls.TreeNode
            Dim my_DataView As DataView = New DataView
            my_DataView.Table = my_dataset.Tables(0)
            my_DataView.RowFilter = "parent_id = 0"
 
            For Each my_row As DataRowView In my_DataView
                TreeNode = New Microsoft.Web.UI.WebControls.TreeNode
                TreeNode.Text = my_row("short_name")
                TreeNode.ID = my_row("id")
                add_sub_MenuItems(TreeNode)
                Treeview1.Nodes.Add(TreeNode)
            Next
            HttpContext.Current.Session("my_TreeView") = Treeview1
        Else
            Dim Treeview_tmp As Microsoft.Web.UI.WebControls.TreeView = HttpContext.Current.Session("my_TreeView")
            Treeview1 = Treeview_tmp
        End If
        treeview_inpage = TreeView1 'here is my problem : the treeview_inpage-object is well filled (tested it with treeview_inpage.Nodes.Count), but it keeps blanc at the output...
    End Function
    Private Function add_sub_MenuItems(ByRef parent_TreeNode As Microsoft.Web.UI.WebControls.TreeNode)
        Dim TreeNode As Microsoft.Web.UI.WebControls.TreeNode
        Dim my_DataView As DataView = New DataView
        my_DataView.Table = my_dataset.Tables(0)
        my_DataView.RowFilter = "parent_id = " & parent_TreeNode.ID
 
        For Each my_row As DataRowView In my_DataView
            TreeNode = New Microsoft.Web.UI.WebControls.TreeNode
            TreeNode.Text = my_row("short_name")
            TreeNode.ID = my_row("id")
            add_sub_MenuItems(TreeNode)
            parent_TreeNode.Nodes.Add(TreeNode)
        Next
    End Function

second code (with placehoder, but I do not know how to manage click-evnets...)

VB Code:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        fill_TreeView()
    End Sub
    Public my_hierarchy As hierarchy
    Public my_dataset As DataSet
    Public Treeview1 As Microsoft.Web.UI.WebControls.TreeView
    Sub New()
        my_hierarchy = HttpContext.Current.Session("my_product_hierarchy")
        my_dataset = my_hierarchy.my_dataset_all_hierarchy_elements
    End Sub
    Public Function fill_TreeView()
        If HttpContext.Current.Session("my_TreeView") Is Nothing Then
            Treeview1 = New Microsoft.Web.UI.WebControls.TreeView
            Dim TreeNode As Microsoft.Web.UI.WebControls.TreeNode
            Dim my_DataView As DataView = New DataView
            my_DataView.Table = my_dataset.Tables(0)
            my_DataView.RowFilter = "parent_id = 0"
 
            For Each my_row As DataRowView In my_DataView
                TreeNode = New Microsoft.Web.UI.WebControls.TreeNode
                TreeNode.Text = my_row("short_name")
                TreeNode.ID = my_row("id")
                add_sub_MenuItems(TreeNode)
                Treeview1.Nodes.Add(TreeNode)
            Next
            HttpContext.Current.Session("my_TreeView") = Treeview1
        Else
            Dim Treeview_tmp As Microsoft.Web.UI.WebControls.TreeView = HttpContext.Current.Session("my_TreeView")
            Treeview1 = Treeview_tmp
        End If
        PlaceHolder2.Controls.Add(Treeview1) ' when I use a placeholder like this it works, but I have a problem to deal with click-events...
    End Function
    Private Function add_sub_MenuItems(ByRef parent_TreeNode As Microsoft.Web.UI.WebControls.TreeNode)
        Dim TreeNode As Microsoft.Web.UI.WebControls.TreeNode
        Dim my_DataView As DataView = New DataView
        my_DataView.Table = my_dataset.Tables(0)
        my_DataView.RowFilter = "parent_id = " & parent_TreeNode.ID
 
        For Each my_row As DataRowView In my_DataView
            TreeNode = New Microsoft.Web.UI.WebControls.TreeNode
            TreeNode.Text = my_row("short_name")
            TreeNode.ID = my_row("id")
            add_sub_MenuItems(TreeNode)
            parent_TreeNode.Nodes.Add(TreeNode)
        Next
    End Function