使用jquery 获取RadioButtonList 中选中值

<mce:script language="javascript"><!--  
        $(document).ready(function() {  
 
            $("#btnSubmit").click(function() {  
 
                alert($("#RadioButtonList1").find("input[@checked]").val());  
 
            });  
 
        });  
 
      
// --></mce:script>  
 
   
 
<asp:RadioButtonList ID="RadioButtonList1" runat="server">  
 
        <asp:ListItem>1</asp:ListItem>  
 
        <asp:ListItem>2</asp:ListItem>  
 
        <asp:ListItem>3</asp:ListItem>  
 
    </asp:RadioButtonList>  
 
     <input id="btnSubmit" type="button" value="Submit" />