Calculating Fields
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Delphi puts a dataset into dsCalcFields mode whenever an application calls the dataset’s OnCalcFields event handler. This state prevents modifications or additions to the records in a dataset except for the calculated fields the handler is designed to modify. The reason all other modifications are prevented is because OnCalcFields uses the values in other fields to derive values for calculated fields. Changes to those other fields might otherwise invalidate the values assigned to calculated fields.
When the OnCalcFields handler finishes, the dataset is returned to dsBrowse state.
For more information about creating calculated fields and OnCalcFields event handlers, see Using OnCalcFields.