You can try either of these options (Untested):
1. Using JavaScript
function ValidateRadioButton(sender, args)
{
var repeater = document.getElementById("<%= YourRepeaterID.ClientID %>");
var items = repeater.getElementsByTagName('input');
for (var i = 0; i < items.length; i++)
{
if (items[i].type == "radio")
{
if (items[i].checked)
{
args.IsValid = true;
return;
}
else
{
args.IsValid = false;
}
}
}
}
2. Using jQuery
function ValidateRadioButton(sender, args)
{
$(':input').each(function () {
var $e = $(this);
if(($e.is(':radio')) && $e.prop('checked')) {
args.IsValid = true;
return;
} else {
args.IsValid = false;
}
});
}
You can then call the function
ValidateRadioButton()
in your
CustomValidatior
like this:
<asp:customvalidator id="CustomValidator2" runat="server" errormessage="Selection is required" clientvalidationfunction="ValidateRadioButton"/>