Set ASP.Net DropDownList selected value from Session variable

Please help i would like to click back and the get the current dropdown values and save them to the next page how can i achive this please help

Session("holder") = "Back"
Session("Class") = ddlclass.SelectedItem.Text
Session("Stream") = ddlstream.SelectedItem.Text
Session("Term") = ddlterm.SelectedItem.Text
Response.Redirect(String.Format("~/Forms/CommentingPre.aspx"))

This is the webpage where i what to save the values from previous wepage

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

        If Session("holder") = "FirstLoad" Then

            If Not Me.IsPostBack Then
                BindGrid400()
            End If
        Else

            If Session("holder").ToString = "Back" Then
                Classdll.SelectedValue = Session("Class").ToString
                ddlterm.SelectedValue = Session("Term").ToString
                Streamddl.SelectedValue = Session("Stream").ToString

                ' If Not Me.IsPostBack Then
                BindGrid4005()
                ' Dim kk As String
                ' kk = Session("Class").ToString
                'Classdll.Items.FindByValue("Class").Selected = True
                'Streamddl.Items.FindByValue("Stream").Selected = True
                ' End If
            End If
            End If

    End Sub

this is what iam using save the values but when debugging the sessions show that they have the save record but when i try to assign it i get

Classdll.SelectedValue
ddlterm.SelectedValue 
Streamddl.SelectedValue