I have a requirement to validate an email address and web address for basic format validity in a custom grid popup. All standard data annotated validation works such as required, length etc in the popup but adding the validation for the email address and web address by implementing the IValidatableObject interface on my model and adding the necessary code in a Validate method doesn't produce the required effect. At first pass, the popup closes and an error is displayed at the bottom of the grid view (as it would with an inline editable grid). I've followed the example code provided, albeit for MVC, to handle server side validation errors in the Error event of the datasource of the grid and while it stops the popup from closing, it will not display the error messages against the relevant controls - in fact it displays nothing at all. I've not been able to debug the message handling code to establish why it is not able to connect the error message (correctly returned) with the relevant control of the popup. Can you please advise?