Checking if a databound radiobutton is empty

Hello,

How do i check to see if a databound radiobutton control is empty ?

Below is my radiobutton control, am using an objectdatasouce to bind it.

Thanks

 

<asp:RadioButtonList ID="RadioButtonList_groups" runat="server"
BorderColor="#999999" BorderStyle="Solid" BorderWidth="1px" CellSpacing="2"
DataSourceID="ObjectDataSource_PhoneGroups" DataTextField="Groupname" 
DataValueField="name" style="text-align: left; background-color: #FFFFFF">
</asp:RadioButtonList>
...