duplicate nodes

[rayala25]

Hello,  I'm following sample of treeview LoadOnDemand,  i want to fill a tree with categories-subcategories data, but when i expand a categories node, it fills subcategories but it duplicates them. 

Using   ASP.NET AJAX Q2 2008 , WXP,  VS2008, VB  the code is a follows...

UPDATE:  Debugging the project ,  i know  "RadTreeView1_NodeExpand"  is fired twice , why is this happening?  or what can i do to fire this event just one time?

    Sub FillTree()
        Dim connection As New SqlConnection(System.Configuration.ConfigurationManager.AppSettings("ConStr2"))
        Dim selectCommand As New SqlCommand("SELECT * FROM Categorias WHERE Codigo > 0", connection)
        Dim adapter As New SqlDataAdapter(selectCommand)
        Dim data As New DataTable()
        adapter.Fill(data)
        For Each row As DataRow In data.Rows
            Dim node As New RadTreeNode()
            node.Text = row("Descripcion")
            node.Value = row("Codigo")
            node.ExpandMode = TreeNodeExpandMode.ServerSideCallBack
            RadTreeView1.Nodes.Add(node)
        Next
    End Sub

    Sub RadTreeView1_NodeExpand(ByVal sender As Object, ByVal e As RadTreeNodeEventArgs) Handles RadTreeView1.NodeExpand
        Dim connection As New SqlConnection(System.Configuration.ConfigurationManager.AppSettings("ConStr2"))
        Dim selectCommand As New SqlCommand("SELECT Children.Codigo as NodeId, Children.Descripcion AS NodeText, COUNT(Children.Codigo) AS ChildCount FROM Categorias LEFT JOIN Familias As Children ON Categorias.Codigo = Children.Categoria WHERE Children.Categoria = @parentId GROUP BY Children.Codigo, Children.Descripcion", connection)
        selectCommand.Parameters.AddWithValue("parentId", e.Node.Value)
        Dim adapter As New SqlDataAdapter(selectCommand)
        Dim data As New DataTable()
        adapter.Fill(data)
        For Each row As DataRow In data.Rows
            Dim node As New RadTreeNode()
            node.Text = row("NodeText")
            node.Value = row("NodeId")
            If CInt(row("ChildCount")) > 0 Then
                node.ExpandMode = TreeNodeExpandMode.ServerSideCallBack
            End If
            e.Node.Nodes.Add(node)
        Next
        e.Node.Expanded = True
    End Sub

Thanks for any help. 

[rayala25]

Please any help!