Send retained transaction descriptor in MARS TDS header for .NET Core and .NET 5+

[swh-cb]

The retained transaction descriptor (TdsParser._retainedTransactionId) is send in the MARS TDS header for .NET Core and .NET 5+ applications when a distributed MSDTC transaction is explicitly rolled back without defecting. The retained transaction descriptor must be sent to the server on subsequent executions even though the transaction is considered to be rolled back. The .NET Framework driver already sends the retained transaction descriptor in this case (see here).

Fixes #1623

[Wraith2]

Looks like a straightforward fix and improvement. Have you checked to make sure that the _retainedTransactionId field is correctly zeroed when the transaction is finished with?

[swh-cb]

Yes, the _retainedTransactionId field is cleared (SqlInternalTransaction.NullTransactionId) in the following cases:

• Connection is enlisted in null transaction or a new transaction (Begin or Propagate for TransactionManagerRequest request)
• Notification from the server of a new transaction (ENV_BEGINTRAN or ENV_ENLISTDTC for ENVCHANGE notification)
• Notification from the server that a server-side transaction ends by anything other than rollback (ENV_DEFECTDTC, ENV_TRANSACTIONENDED or ENV_COMMITTRAN for ENVCHANGE notification)

[David-Engel]

LGTM