Validation rules are criteria that a DataWindow object uses to validate data entered into a column by users. They are DataWindow .NET-specific and therefore not enforced by the DBMS.
Validation rules assigned in the Database painter are used by default when you place columns in a DataWindow object. You can override the default rules in the DataWindow painter.
A validation rule is an expression that evaluates to either true or false. If the expression evaluates to TRUE for an entry into a column, DataWindow Designer accepts the entry. If the expression evaluates to false, the entry is not accepted and the ItemError event is triggered. By default, DataWindow Designer displays a message box to the user. You can customize the message displayed when a value is rejected.
You can also code the ItemError event to cause different processing to happen.
For more information, see the chapter on using DataWindow objects in the Programmer’s Guide.
