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

ADOFields Collections and ADOField Objects

Recordset objects contain a collection of field objects used to work with the individual columns of the rowset. Each column that is returned in the recordset has an associated ADOField object in this collection. The Field object gives you access to column metadata, such as the column name and data type, and the actual value for the column in the current row.

ADOFields Collection Members

The ADOFields collection includes a Count property, which gives the number of individual Field objects in the collection, and an Item property, which is used to retrieve individual Field objects. In addition, the Fields collection includes a Refresh method, although this has no real effect on the Fields collection.

ADOField Object Properties

Each of the individual ADOField objects has the following properties:

• ActualSize indicates the actual length of the data for the current row's value.
• Attributes contains a group of settings for this column, including its updatability, nullability, and other information.
• DefinedSize indicates the maximum size allotted for a value of this column.
• Name indicates the name of the column. You can access individual fields in the collection either by this name or by their ordinal value.
• NumericScale indicates how many places to the right of the decimal point are used to represent this value.
• OriginalValue contains the original value of the column as it was last fetched from the data source, prior to any changes you have made.
• Precision indicates the maximum number of digits used to represent the value for numerical columns.
• Type gives the type of data used for values in this column.
• UnderlyingValue reflects the current value of the column in the datasource. This can differ from the Value and OriginalValue properties because of changes made by other applications since the row was originally fetched.
• Value contains a VARIANT holding the current data value for this column of the current row in the recordset.

ADOField Object Methods

Each ADOField object also implements the following methods:

• AppendChunk is used to add portions of long data objects to the datasource, enabling you to work with blocks of data smaller than the entire value.
• GetChunk is used to retrieve large data objects in smaller, more manageable pieces.

Share This