TCustomValidator performs user-defined validation (either
server-side or client-side or both) on an input component.
To create a server-side validation function, provide a handler for
the {@link onServerValidate OnServerValidate} event that performs the validation.
The data string of the input control to validate can be accessed
by {@link TServerValidateEventParameter::getValue Value} of the event parameter.
The result of the validation should be stored in the
{@link TServerValidateEventParameter::getIsValid IsValid} property of the event
parameter.
To create a client-side validation function, add the client-side
validation javascript function to the page template.
The function should have the following signature:
Use the {@link setClientValidationFunction ClientValidationFunction} property
to specify the name of the client-side validation script function associated
with the TCustomValidator.