Show dynamically generated RadioButtonList selected item in Label using VB.Net

Hi,

I am getting this error (Object reference not set to an instance of an object.) at

lbl_variant_option_selected.InnerText = rbl.SelectedItem.Attributes("variant_name")

when i try to show selected item from radiobuttonlist. Any idea?

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        createRBLcontrols()

    End Sub

    Private Sub createRBLcontrols()


            Dim rbl As New RadioButtonList
        rbl.ID = "rbl_product_option1"

            rbl.Items.Add("Red")
            rbl.Items(0).Attributes.Add("variant_name", "Red")

            rbl.Items.Add("Blue")
            rbl.Items(1).Attributes.Add("variant_name", "Blue")

            rbl.Items(0).Selected = True

            Dim titleDiv As New System.Web.UI.HtmlControls.HtmlGenericControl("div")
        titleDiv.ID = "titleDiv"
        titleDiv.InnerHtml = "<div class=""wrap"">Color:&nbsp;<span id='lbl_variant_option_selected' runat='server'>Red</span></div>"
            Me.ContainerRBL.Controls.Add(titleDiv)


            rbl.RepeatDirection = RepeatDirection.Horizontal


        rbl.AutoPostBack = True

            AddHandler rbl.SelectedIndexChanged, AddressOf SelectedIndexChanged_rbl
            Me.ContainerRBL.Controls.Add(rbl)

    End Sub

    Private Sub SelectedIndexChanged_rbl(ByVal sender As Object, ByVal e As EventArgs)

        For i As Integer = 0 To Me.ContainerRBL.Controls.Count - 1

            Dim lbl_variant_option_selected As System.Web.UI.HtmlControls.HtmlGenericControl = CType(Me.FindControl("lbl_variant_option_selected"), System.Web.UI.HtmlControls.HtmlGenericControl)

            Dim rbl As RadioButtonList = Me.ContainerRBL.FindControl("rbl_product_option1")
            If IsNothing(rbl) = False Then

                lbl_variant_option_selected.InnerText = rbl.SelectedItem.Attributes("variant_name")

            End If
        Next
    End Sub