找Repeater里面的控件-findcontrol使用求救

这是前台代码：
<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="show.aspx.cs" Inherits="show" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <style type="text/css">
        .style4
        {
            width: auto;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:LinkButton ID="LinkButton3" runat="server" Visible="false"><a href="leaveword.aspx">我要留言&nbsp;&nbsp;</a></asp:LinkButton>
        <asp:LinkButton ID="LinkButton1" runat="server" Visible="false"><a href="memberlogin.aspx">登录&nbsp;&nbsp;</a></asp:LinkButton>
        <asp:LinkButton ID="LinkButton2" runat="server" Visible="false"><a href="login.aspx">注册</a></asp:LinkButton>
        <br />
        <br />
        <asp:Repeater ID="Repeater1" runat="server" DataSourceID="SqlDataSource1" >
        <ItemTemplate>
         <table id="table1" runat="server" class="style4">
            <tr>
                <td class="style4">
                    标题：<%# DataBinder.Eval(Container.DataItem,"title") %>&nbsp;&nbsp;&nbsp;</td>
                <td>
                    <%# DataBinder.Eval(Container.DataItem,"name") %>于<%# DataBinder.Eval(Container.DataItem,"date") %>发表</td>
            </tr>
            <tr>
                <td colspan="2">
                    留言：<%# DataBinder.Eval(Container.DataItem,"word") %></td>
            </tr>
            <tr>
                <td colspan="2">
                    <asp:HyperLink ID="Button1" Visible="false" runat="server" NavigateUrl='<%#"?act=1&id="+Eval("id")%>'>查看回复</asp:HyperLink>
                    <asp:HyperLink ID="Button3" Visible="false" runat="server" NavigateUrl='<%#"?act=2&id="+Eval("id")%>'>收起回复</asp:HyperLink>
                </td>
            </tr>
            <tr>
            <td>
            
            <asp:Panel runat="server" ID="Panel1" visible="false">
            <table id="table2" runat="server" class="style4" >
            <tr>
            <td>
            <asp:TextBox ID="TextBox1" runat="server" Height="41px" TextMode="MultiLine" Width="1005px"></asp:TextBox></td>
            </tr>
            <tr>
            <td>
            <asp:Button ID="Button2" runat="server" Text="回复" onclick="Button2_Click" CommandArgument = '<%# DataBinder.Eval(Container.DataItem,"id") %>'  CommandName="Reply"/></td>
            </tr>
            <tr>
            <td>
            <asp:Repeater ID="Repeater2" runat="server" >
            <ItemTemplate>
            <table id="table3" runat="server" class="style4">
            <tr>
            <td>
            <%# DataBinder.Eval(Container.DataItem,"name") %>:<%# DataBinder.Eval(Container.DataItem,"word") %>(<%# DataBinder.Eval(Container.DataItem,"date") %>)
            </td>
            </tr>
            </table>
            </ItemTemplate>
            </asp:Repeater>
            </td>
            </tr>
            </table>
            </asp:Panel>            </td>
            </tr>
            </table>
            <br />
        </ItemTemplate>
        </asp:Repeater>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
            ConnectionString="<%$ ConnectionStrings:leavewordConnectionString4 %>" 
            SelectCommand="SELECT * FROM [leaveword]"></asp:SqlDataSource>
    </div>
</form>
</body>
</html>
这里是后台的Page_Load：protected void Page_Load(object sender, System.EventArgs e)
    {
        Panel Panel1 = this.Repeater1.FindControl("Panel1") as Panel;
        HyperLink Button1 = this.Repeater1.FindControl("Button1") as HyperLink; 
        HyperLink Button3 = this.Repeater1.FindControl("Button3") as HyperLink; 
        Repeater Repeater2 = this.Repeater1.FindControl("Repeater2") as Repeater;         //Panel Panel1 = (Panel)this.Repeater1.FindControl(string.Format("Panel1{0}", ""));
        //HyperLink Button1 = (HyperLink)this.Repeater1.FindControl(string.Format("Button1{0}", "")); 
        //HyperLink Button3 = (HyperLink)this.Repeater1.FindControl(string.Format("Button3{0}", "")); 
        //Repeater Repeater2 = (Repeater)this.Repeater1.FindControl(string.Format("Repeater2{0}", ""));         //Panel Panel1 = this.Page.FindControl("Panel1") as Panel;
        //HyperLink Button1 = this.Page.FindControl("Button1") as HyperLink;
        //HyperLink Button3 = this.Page.FindControl("Button3") as HyperLink;
        //Repeater Repeater2 = this.Page.FindControl("Repeater2") as Repeater;
        //Items[0]        if (Session["membername"]==null)
        {
            LinkButton1.Visible = true;
            LinkButton2.Visible = true;
        }
        else
        {
            LinkButton3.Visible = true;
            Button1.Visible = true;
        }
        
        if (!IsPostBack)
        {
            string act = Request.QueryString["act"];
            string leavewordid = Request.QueryString["id"];
            string str1 = "Data Source=(local);Initial Catalog=leaveword;integrated security=True";
            switch (act)
            {
                case "1":
                    SqlConnection conn = new SqlConnection(str1);
                    conn.Open();
                    DataSet ds2 = new DataSet();
                    string str2 = "Select leavewordid From [reply] Where leavewordid='" + leavewordid + "'";
                    SqlDataAdapter da2 = new SqlDataAdapter(str2, conn);
                    da2.Fill(ds2, "t1");
                    Repeater2.DataSource = ds2.Tables["t1"];
                    Repeater2.DataBind();                    Panel1.Visible = true;
                    Button1.Visible = false;
                    Button3.Visible = true;
                    conn.Close();
                    break;
                case "2":
                    Panel1.Visible = false;
                    Button1.Visible = true;
                    Button3.Visible = false;
                    break;
                default:
                    Panel1.Visible = false;
                    Button1.Visible = false;
                    Button3.Visible = false;
                    break;
            }
        }
    }
然后无论用哪种FindControl找到的值都为null，求高手帮助~