Cross-field Validation function is used to validate multiple fields in a form if their values are correlative. Submit type buttons in the form will be disabled until all the defined cross-field validations for the form are valid. For example, on most user account register forms, there are two password input fields. In order to avoid user inputting wrong password accidentally, these two fields are required to have the same value before the form can be submitted.
When any field in the form is changed (lost focus), the form would invoke the validation. When a cross-field validation rule is not valid, and there is no single-field validation message need to be shown, the hint message of the invalid cross-field validation rule will be shown.
If a form has multiple cross-field validation rules, and more than one rules are not valid, only one hint message of invalid rule will be selected and shown on the form. The message of invalid rules is selected according to: