Mandatory falg on form data source field with disabled configuration key

There's a design bug with the form data source field property called mandatory. If you set it to true, the condition if the field is filled in will be checked even the field is deactivated by configuration.

As an example: Your table TableA has two fields: FieldA and FieldB. FieldB has configuration key property value ConfigKeyA. You create a form with a data source from table TableA. You set the data source field FieldB's property mandatory to true. Now you go to administration/settings/system/configuration and deactivate configuration key ConfigKeyA. At least restart client, open the created form and try to save a new record. It will fail with the message that field FieldB has to be filled in.

So be careful if manipulating the mandatory property on form data source fields.

This applies to AX 2009, but I have not tested if it applies to former Versions too.