In ABL, you can define indexes for temp-tables, one of which can be marked as the primary index. An index can consist of one of more fields in the temp-table.

.NET DataTables can only represent unique indexes (unique primary indexes and unique non-primary indexes).

If an ABL procedure has a temp-table parameter or a ProDataSet parameter (which contains temp-tables) and a temp-table has one or more unique indexes, the resulting .NET DataTable has a UniqueConstraint object for each index. For the primary index, its corresponding UniqueConstraint.PrimaryKey property is set to true. All other non-unique indexes are ignored because there is no corresponding .NET constraint to which they can be mapped.

For more information on .NET DataTable constraints, see the Microsoft .NET documentation.