Elegant way to make CustomValidator work with ValidationSummary messagebox

Question

I have run into this problem before but never quite solved it. I have a form with several validators and also a CustomValidator.

Answer 1

I have found a workaround for when javascript is disabled and the ValidationSummary does not show the errorMessage property of the CustomValidator. This is required as injecting script or alerts, as described above, will not work.

Add a new Validator control, let's call it CustomValidatorProxy, set its ControlToValidate property to any one of the controls on the form and EnableClientScript=false.

Within the ServerValidate event handler perform your custom validation and if validation fails set the IsValid property of the CustomValidator and CustomValidatorProxy to false and similarly set both ErrorMessage properties.

If the validation in the ServerValidate is passed ensure that the IsValid property of the CustomValidatorProxy is set to true.

Provided the CustomValidatorProxy is before the CustomValidator in the ValidatorCollection of the Page then the ServerValidate handler will override the IsValid property value that the CustomValidatorProxy would have returned having validated the ControlToValidate value and your ErrorMessage from your CustomValidator will be displayed in the ValidationSummary.