Passing querystring problem

Can anyone see anything wrong with the following:
 passing page:

  Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim url As String = [String].Format("SearchResults.aspx?category={0}", ddlcategory.SelectedValue)
        Response.Redirect(url)
    End Sub
 resulting url :  http://localhost:2421/website/SearchResults.aspx?category=2

 receiving page:
 Partial Class SearchResults
    Inherits BasePage

    Dim sLName As String
    Sub Page_Load()
        sLName = Request.QueryString("category")
        TextBox4.Text = sLName
    End Sub

End Class
and yet ...