Hi
Once radiobuttonlist render to client its unable to call server side event for control like radiobuttonlist.Also it will make performance impact.Best way is
Register client side onclick event and you can get radionbutton object with selected item
save it in hiddenfield and then on server click use that values.
<asp:radiobuttonlist id="rdlLst" runat="server" onselectedindexchanged="IndexChanged" xmlns:asp="#unknown">
<asp:listitem text="1" onclick="Test(this);"></asp:listitem>
<asp:listitem text="2"></asp:listitem>
<asp:listitem text="3"></asp:listitem>
</asp:radiobuttonlist>
<script type="text/javascript">
function Test(obj)
{
alert('here');
}
</script>
Please let me know if this helpful.