Behind code problem

Hi guys i'm new to this forum and new to ASP.

However not new to programming (I know PHP & abit of Java)

I'm currently stuck on a little something i'm working on. As far as I understand you can have a 'behind code' aspx.vb file which basically seperates your logic from your views.

So I have a page default.aspx.vb with this in it:

Public Class _Default
    Inherits System.Web.UI.Page

    Public adult As String
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        adult = "test"
    End Sub

End Class

and a default.aspx with this:

<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="DatabaseExample._Default" %><%@ Import Namespace="System.Data.OleDb"%><%= adult %>

As I understand adult should already be declared and available for use in my normal .aspx file

Why is it i'm still getting this error stating it's undeclared:

Compiler Error Message: BC30451: 'adult' is not declared. It may be inaccessible due to its protection level.a

Can somebody explain this to me please?