Microsoft KB Archive/160074

= SetFieldNull Asserts or Crashes When Called for Parameter =

Article ID: 160074

Article Last Modified on 8/9/2004

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APPLIES TO

 Microsoft Foundation Class Library 4.2, when used with:  Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 4.2 Professional Edition 

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This article was previously published under Q160074



SUMMARY
CRecordset::SetFieldNull causes an assert or an access violation if called for a parameter. Even if no assert or access violation occurs, the parameter may not be set to Null.

If SetFieldNull is called before the recordset is open, the assert occurs in DBRFX.CPP at line 48: ASSERT(prs->m_hstmt != SQL_NULL_HSTMT); If SetFieldNull is called after the recordset is open, then a call to CRecordset::Requery may assert in DBCORE.CPP at line 4055 or line 4062: ASSERT(nParam < m_nParams); If SetFieldNull is called after the recordset is closed and before it is reopened, you will see an access violation in DBCORE.CPP at line 4057: m_pbParamFlags[nParam] |= AFX_SQL_FIELD_FLAG_NULL; or at line 4064: m_pbParamFlags[nParam] &= ~AFX_SQL_FIELD_FLAG_NULL; NOTE: Visual C++ 5.0 has a new function called SetParamNull that you can use to avoid this problem. SetFieldNull in Visual C++ 4.2 was not designed to be called before calling CRecordset::Open, and was not designed to handle parameters. The following files are available for download from the Microsoft Download Center:

Paramset.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.

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. The problem has been fixed with Visual C++ version 5.0 by adding a new function called SetParamNull.



MORE INFORMATION
Once you have downloaded Paramset.exe and run the EXE to extract the CParamSet class files, add CParamSet.CPP to your project.

Change your recordsets to be derived from CParamSet rather than CRecordset.

CRecordset::SetFieldNull cannot be called before the recordset is open. If you want to call SetFieldNull to set parameters to Null before calling CRecordset::Open, then call CParamSet::SetParamNull instead. You will have to change the parameters that are passed to SetParamNull because SetFieldNull requires a pointer to the parameter and SetParamNull requires a zero-based index.

In your implementation of the DoFieldExchange function, change each call to an RFX function for a parameter to a call to the corresponding Param_RFX function.

