Hi, i have a problem with adding nodes
Here is my code.

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        If Not IsPostBack Then

            Dim cn As New SqlConnection(cnString)
            Dim cmd As New SqlCommand
            Dim objReader As SqlDataReader
            Dim strSQL As String

            strSQL = "select ID, NAME from Table1"
            With cmd
                .Connection = cn
                .CommandType = CommandType.Text
                .CommandText = strSQL
            End With

            cn.Open()
            objReader = cmd.ExecuteReader
            Dim n As New TreeNode

            While (objReader.Read)
                n.Text = objReader.Item("Name")
                n.ImageUrl = "bs.gif"
                n.Expandable = ExpandableValue.Always
                n.ExpandedImageUrl = "bo.gif"
                n.NodeData = objReader.Item("ID")
                tvwHelp.Nodes.Add(n)
            End While
        End If
    End Sub 'This is ok but I have a problem with next
'''''''''''''''''''''''''''''''''''''''''''''''''' '''''''''''''''''''''''''''''''''''''''''''''''''' ''

Private Sub tvwHelp_Expand(ByVal sender As Object, ByVal e As Microsoft.Web.UI.WebControls.TreeViewClickEventArg s) Handles tvwHelp.Expand

        Dim cn As New SqlConnection(cnString)
        Dim cmd As New SqlCommand
        Dim objReader As SqlDataReader
        Dim strSQL As String
        Dim nE As TreeNode
        Dim nodeRez As TreeNode

        nE = sender.nodes(e.Node.ToString)

        If nE.Nodes.Count = 0 Then

            strSQL = " select ID,SINAME as NAME from TOC " _
            & " where PARENTID =" & CInt(nE.NodeData.ToString) "

            With cmd
                .Connection = cn
                .CommandType = CommandType.Text
                .CommandText = strSQL
            End With

            cn.Open()
            objReader = cmd.ExecuteReader

            While objReader.Read
                nodeRez = New TreeNode
                nodeRez.Text = objReader.Item("Name")
                nodeRez.NodeData = objReader.Item("ID")
                nodeRez.Expandable = ExpandableValue.Always
                nE.Nodes.Add(nodeRez)
            End While
        Else
            nE.Expanded = True
        End If
    End Sub
''''''''''''''''''''''''
 tvwHelp_Expand works fine only for first time, but later when i want to expand any other child node i always get error:

 System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. Parameter name: Index was out of range. Must be non-negative and less than the size of the collection.

How can i solve this problem?
Thanks very much