js改变Lable的innerText后，怎样在后台代码中获得Lable的值

    <script>
        function test() {
            document.getElementById("Label1").innerHTML = "fdsfds";
            document.getElementById("hid").value = document.getElementById("Label1").innerHTML;
        }
   </script>
   <input type="button" onclick="test()" value="test">
   <asp:Label id="Label1" runat="server">Label</asp:Label>
   <input type=hidden id="Hidden1" runat=server>

后台用:string str=this.hid.Value;取值.