questo un altro modo
codice:
    Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
        If Not Me.IsPostBack Then
            'popolo il DropDown leggendo i dati da database
            'trasformando le date tipo 20170107 in 07/01/2017
            Dim result = ora.GetDataTable(gl.StringaConnessioneORA_PIETRO, "SELECT ID, DATA FROM A").AsEnumerable.
                OrderBy(Function(r) r("data")).
                Select(Function(r) New With {.id = CInt(r("id")), .data = NumberToDate(CInt(r("data"))).ToString("d")})

            Me.DropDownList1.DataSource = result
            Me.DropDownList1.DataTextField = "data"
            Me.DropDownList1.DataValueField = "id"
            Me.DropDownList1.DataBind()

        End If
    End Sub