Changing A Site's Culture Programmatically

i'm trying to set my website's culture programmatically, so when a user clicks a button they can change the text on the page from english to spanish. here's my code:

protected void btnChangeLanguage(object sender, EventArgs e)
{
Thread.CurrentThread.CurrentCulture = new CultureInfo("es");
Thread.CurrentThread.CurrentUICulture = new CultureInfo("es);
}
<asp:Label ID="lblDisplay" runat="server" meta:ResourceKey="lblDisplay" />
<asp:Button ID="btnChangeLanguage" runat="server" Text="Change Language"
OnClick="btnChangeLanguage_Click" />

i have a Default.aspx.resx file with a key/value of: lblDisplay.text/English and a Default.aspx.es.resx file with a key/value of: lblDisplay.text/Espanol. i can't get my Label's text to change from "English" to "Spanish". anyone see what i'm doing wrong?