Our good friend Peter Blum
recently announced official support
for our upcoming RadControls for ASP.NET AJAX
(aka "Prometheus"). All customers that are using his Data Entry Suite
will be able to integrate validation into the Telerik controls almost invisibly and without much pain and effort.
For those of you that are not familiar with Peter Blum, he is an ASP Insider and the author of the BEST set of validation controls on the market. I don't have any reservations to recommend his products as they are well done, very stable and very well documented.