Unfortunately, with DocuWare 7.xx it is still not possible to validate changes made in index dialogs using a validation service, as only the changed data is reported to the service, not the index data that was in the index dialog before the change. The validation service cannot therefore react to index changes in certain fields, but can only analyze the new data to be written.
If, for example, you want to write a validation that only allows a document status to be changed to the value "paid" if the status was previously "approved", this is not possible, as the service does not receive any information about what content the index field document status had before the change.
I therefore suggest that the request that triggers the validation sends the data that was present before the index dialog was changed, in addition to the data that is in an index dialog after a change.
This would also correspond to the validation implementation that was possible with DocuWare 6 via the DocuWare.ValidatorBase.dll.
When transmitting the validation request from a storage dialog, the values for before and after the index change could be identical, since in principle no index change occurs during storage. Alternatively, the values could simply remain empty (NULL).