Visual C++ 6 Unleashed

By MICKEY WILLIAMS and David Bennett

• Table of Contents
  • Copyright
  • About the Authors
  • About the Contributors
  • Acknowledgments
  • Tell Us What You Think!
  • Introduction
  • How to Use This Book
  • What You Need to Use This Book
  • What's New in Visual C++ 6.0
  • Contacting the Main Author
  • Part I: Introduction
  • Chapter 1. The Visual C++ 6.0 Environment
  • Part II: MFC Programming
  • Chapter 2. MFC Class Library Overview
  • Chapter 3. MFC Message Handling Mechanism
  • Chapter 4. The Document View Architecture
  • Chapter 5. Creating and Using Dialog Boxes
  • Chapter 6. Working with Device Contexts and GDI Objects
  • Chapter 7. Creating and Using Property Sheets
  • Chapter 8. Working with the File System
  • Chapter 9. Using Serialization with File and Archive Objects
  • Part III: Internet Programming with MFC
  • Chapter 10. MFC and the Internet Server API (ISAPI)
  • Chapter 11. The WinInet API
  • Chapter 12. MFC HTML Support
  • Part IV: Advanced Programming Topics
  • Chapter 13. Using the Standard C++ Library
  • Chapter 14. Error Detection and Exception Handling Techniques
  • Chapter 15. Debugging and Profiling Strategies
  • Chapter 16. Multithreading
  • Chapter 17. Using Scripting and Other Tools to Automate the Visual C++ IDE
  • Part V: Database Programming
  • Chapter 18. Creating Custom AppWizards
  • Chapter 19. Database Overview
  • Chapter 20. ODBC Programming
  • Chapter 21. MFC Database Classes
  • Chapter 22. Using OLE DB
  • Chapter 23. Programming with ADO
    • ADO Objects
    • Connection Objects
    • ADOCommand Objects
    • ADORecordset Objects
    • ADOFields Collections and ADOField Objects
    • ADOParameter Objects and the ADOParameters Collection
    • ADOProperty Objects and ADOProperties Collections
    • Writing a Visual C++ ADO Application
    • Processing ADO Errors
    • Enhanced ADO Recordset Functionality
    • Executing Commands
    • Transactions
    • Summary
  • Part VI: MFC Support for COM and ActiveX
  • Chapter 24. Overview of COM and Active Technologies
  • Chapter 25. Active Documents
  • Chapter 26. Active Containers
  • Chapter 27. Active Servers
  • Chapter 28. ActiveX Controls
  • Part VII: Using the Active Template Library
  • Chapter 29. ATL Architecture
  • Chapter 30. Creating COM Objects Using ATL
  • Chapter 31. Creating ActiveX Controls Using ATL
  • Chapter 32. Using ATL to Create MTS and COM+ Components
  • Part VIII: Finishing Touches
  • Chapter 33. Adding Windows Help
  • Part IX: Appendix

Transactions

Transactions enable you to perform several different operations on a database that are executed as a single, atomic operation. This is very useful in cases in which you want to update several tables, but only if all the updates are performed successfully. Transactions can help you avoid the ill effects of partially completed operations if one of the updates should fail.

To begin a transaction on a connection, call its ADOConnection.BeginTrans() method, which takes no parameters. You can then perform any changes to the datasource that you want to be a part of the transaction.

If all goes well and you want to save all the changes to the database, you should call the connection's ADOConnection.CommitTrans() method. If something goes wrong or you just change your mind, you can call ADOConnection.RollbackTrans(), which will undo any changes since the call to ADOConnection.BeginTrans().

After you call ADOConnection.CommitTrans() or ADOConnection.RollbackTrans() to end a transaction, ADO might not automatically start a new transaction for you. This is controlled by setting the Attributes property of the ADOConnection. If you include adXactCommitRetaining in Attributes, a new transaction will be started for you after a call to ADOConnection.CommitTrans(). Similarly, including adXactAbortRetaining starts a new transaction after a call to ADOConnection.RollbackTrans().

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