You do not have to specify this field. In this instance, a default message will be shown. To include the name of the validated editor into the default validation message as a subject, set the name field of the dxValidator object.
If you assign an empty string to the message field, the message will not be shown.
Indicates whether the rule should be always checked for the target value or only when the target value changes.
Set this field to 'custom' to define a rule that will be broken as a result of custom validation performed by the validationCallback function.