Compare A Session Variable With A String In C#?

it still does not work, the user writes appendix then press OK in Login, nothing happens

here is the login (vb.net)

Partial Class login
Inherits System.Web.UI.Page
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Session("passcode") = TextBox1.Text
Response.Redirect("Default.aspx")
End Sub
End Class

and here is the default page C#

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (Session["passcode"] == "appendix")
{
Response.Write("OK !");
}
else
{
Response.Redirect("login.aspx");
}
}
}