跪求一个新手问题！

 <div>
        <asp:ScriptManager runat="server" ID="sm1">
        </asp:ScriptManager>
        <asp:UpdatePanel runat="server" ID="up1" UpdateMode="Conditional" >
            <ContentTemplate>
                <asp:Button id="btn1" runat="server" onclick="btn1_Click"/>
            </ContentTemplate>
        </asp:UpdatePanel>
        <asp:TextBox ID="txt1" runat="server"></asp:TextBox>
        <asp:Button id="btn2" runat="server" onclick="btn2_Click" style="height: 21px"/>
    </div>
我的前台网页代码
 后台单击事件
   protected void btn1_Click(object sender, EventArgs e)
        {
            txt1.Text = "111";
            Response.Write("<script>alert('QQ账号或者密码错误！')</script>");
            
        }        protected void btn2_Click(object sender, EventArgs e)
        {
            txt1.Text = "111";
            Response.Write("<script>alert('QQ账号或者密码错误！')</script>");
        }当我单击btn1进入 btn1_Click了但是里面的代码没效果 是不是放在UpdatePanel里面控件事件去操作前台没用？
 单击btn2里面就有用！