Receipt.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Receipt : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        Label1.Text = Request.QueryString["r"];
        Session.RemoveAll();
    }
}