如何使用FindControl查找内容页上的某个控件？

有以下两个页面Default.aspx和Result.aspx，代码如下：

<!-- Default.aspx -->

<%@ Page Language="C#" AutoEventWireup="true" MasterPageFile="~/Default.master" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<asp:Content ID="Content1" runat="server" ContentPlaceHolderID="ContentPlaceHolder1">

&nbsp;<asp:Label ID="Label1" runat="server" Text="Please input a string here"></asp:Label>

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

<asp:Button ID="Button1" runat="server" Text="Button" PostBackUrl="~/Result.aspx" /></asp:Content>

//Default.aspx.cs

using System;

using System.Data;

using System.Configuration;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

//using System.Web.UI.WebControls.WebParts;