Specifying What Fields Appear in Data Packets
When using a dataset provider, you can control what fields are included in data packets by creating persistent fields on the dataset that the provider uses to build data packets. The provider then includes only these fields. Fields whose values are generated dynamically by the source dataset (such as calculated fields or lookup fields) can be included, but appear to client datasets on the receiving end as static read-only fields.
If the client dataset will be editing the data and applying updates, you must include enough fields so that there are no duplicate records in the data packet. Otherwise, when the updates are applied, it is impossible to determine which record to update. If you do not want the client dataset to be able to see or use extra fields provided only to ensure uniqueness, set the ProviderFlags property for those fields to include pfHidden.
Note: Including enough fields to avoid duplicate records is also a consideration when the provider's source dataset represents a query. You must specify the query so that it includes enough fields to ensure all records are unique, even if your application does not use all the fields.