Jan 13, 2009 12:12 PM|PLBlum|LINK
I recommend both, but consider Server side required. The idea is this:
1. Client-side provides a very interactive user interface, where an edit is immediately followed with a validation error response. It also reduces postbacks.
ASP.NET validation is designed with both of these in mind, and its very easy to use. Drop the necessary controls. On the server side, test Page.IsValid is true before saving the data in a Click method, or if using a different postback event handler, first
call Page.Validate() followed by the test for Page.IsValid.
I strongly recommend you look at my article,
http://aspalliance.com/699. You may also appreciate my tutorial for the deeper aspects of validation at