By default, neither DataReader.GetSchema() nor DataTable.PrimaryKey contains the info of the Primary Key after executing a data select command.

To retrieve Primary Key using DataReader with data, use:

SqlSelectCommand1.ExecuteReader(CommandBehavior.KeyInfo)

To retrieve Primary Key using DataReader without data, use:

SqlSelectCommand1.ExecuteReader(CommandBehavior.KeyInfo Or CommandBehavior.SchemaOnly)

To retrieve Primary Key using DataReader with data, use:

SqlDataAdapter1.MissingSchemaAction = MissingSchemaAction.AddWithKey

SqlDataAdapter1.Fill(ds)

To retrieve Primary Key using DataReader with data, use:

SqlDataAdapter1.FillSchema(ds, SchemaType.Mapped)