<!DOCTYPE html>
<html>
<script  runat="server">
Sub ItemChanged(sender As Object, e As EventArgs)
      lbl1.Text = "You selected " & rb1.Text
End Sub
</script>

<body>

<form runat=server>
<asp:RadioButtonList id="rb1" AutoPostBack="true"
runat="server" OnSelectedIndexChanged="ItemChanged">
      <asp:ListItem Value="Item 1" />
      <asp:ListItem Value="Item 2" />
      <asp:ListItem Value="Item 3" />
      <asp:ListItem Value="Item 4" />
      <asp:ListItem Value="Item 5" />
      <asp:ListItem Value="Item 6" />
</asp:RadioButtonList>
<asp:Label id="lbl1" runat="server"/>
</form>

</body>
</html>