Asynchronous MFC ODBC Database Processing Using Threads (166111)


The information in this article applies to:

  • The Microsoft Foundation Classes (MFC), when used with:
    • Microsoft Visual C++, 32-bit Enterprise Edition 4.2
    • Microsoft Visual C++, 32-bit Enterprise Edition 5.0
    • Microsoft Visual C++, 32-bit Enterprise Edition 6.0
    • Microsoft Visual C++, 32-bit Professional Edition 4.2
    • Microsoft Visual C++, 32-bit Professional Edition 5.0
    • Microsoft Visual C++, 32-bit Professional Edition 6.0
    • Microsoft Visual C++, 32-bit Learning Edition 6.0
    • Microsoft Visual C++ .NET (2002)
This article was previously published under Q166111

SUMMARY

This sample shows how to provide asynchronous database processing by running a database query on a secondary thread.

The following file is available for download from the Microsoft Download Center:

Mtdb.exe

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

NOTE: Use the -d option when running MTDB.EXE to decompress the file and re- create the proper directory structure.

MORE INFORMATION

Beginning with version 4.2 of the MFC database classes, the ability to set the processing mode to asynchronous using CDatabase::SetSynchronousMode() has become obsolete. The MFC ODBC classes now use only synchronous processing.

The following functions, which were used with asynchronous processing in versions before 4.2, are also obsolete: CDatabase::InWaitForDataSource(), CDatabase::OnWaitForDataSource() and CRecordset::OnWaitForDataSource().

One way to implement asynchronous database processing with MFC 4.2 and above is to run your database query on a secondary worker thread. The MTDB sample illustrates this by having each document open the corresponding recordset on a new worker thread. When the user presses the "Cancel Query" button, the primary thread cancels processing on the secondary thread.

As with any multi-threaded database application, each component must be thread-safe. Specifically, you must be using a thread-safe ODBC driver, such as the Microsoft SQL Server ODBC driver, for this application to work correctly.

This sample uses the Student Registration database, which can be created for SQL Server using the STDREG sample program that is included with Visual C++.
Modification Type:MinorLast Reviewed:8/5/2004
Keywords:kbdownload kbDatabase kbfile kbMDACNoSweep kbProgramming kbSample kbThread KB166111
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