XL97: "Unhandled Exception in Mso97.dll" When Using XlCoerce

• Microsoft Excel Software Development Kit 5.0
• Microsoft Excel 97

SYMPTOMS

When you use XlCoerce in a dynamic-link library (DLL) that is loaded by Microsoft Excel 97, the following error message appears

   Unhandled exception in excel.exe (MSO97.DLL): 0xc0000005: Access
   Violation

CAUSE

This problem occurs when the following conditions are true:

• You are using Microsoft Excel 97.

      -and-
  

• The DLL function is called from a worksheet as a result of a calculation.

      -and-
  

• You are attempting to use XlCoerce to coerce a reference XLOPER that refers to a range that contains text.

WORKAROUNDS

To correct this problem, install Microsoft Excel 97 Service Release 1 (SR- 1).

To work around this problem, use one of the following methods.

Method 1

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      /*********
      *  RangeContainsText
      *
      *  Purpose: Determine if a XLOPER reference points to a range that
      *           contains any cells containing text.  Microsoft Excel 97
      *           stops responding if XlCoerce is used to convert a
      *           reference to a string.
      *
      *  Parameter:
      *           pxRange[in]    Range to check.
      *
      *  Return:  TRUE  -  Range contains text, or Excel4 call fails.
      *           FALSE -  Range does not contain text and it is safe to
      *                    use XlCoerce on the reference as a workaround
      *                    to the problem.
      *
      *******************************************************************/
      BOOL RangeContainsText(LPXLOPER pxRange)
      {
         DWORD dwRet = 0;
         XLOPER xIsText;
         BOOL bRet = TRUE;  // Value returned if Excel4 Fails

         // Check determine whether you are working with a range
         if( !((xltypeSRef | xltypeRef) & (pxRange->xltype)))
            return bRet;

         dwRet = Excel4(xlfIstext,&xIsText,1,pxRange);
         if( xlretSuccess == dwRet && xltypeErr != xIsText.xltype)
         {
            XLOPER xRet;
            dwRet = Excel4(xlfOr,&xRet,1,&xIsText);
            if( xlretSuccess == dwRet && xltypeBool == xRet.xltype)
               bRet = xRet.val.bool;
         }
         Excel4(xlFree,0,1,&xIsText);
         return bRet;
      }

Method 2

Instead of using the R data type to pass a range or a cell that may contain text, use the OPER data type (P). This data type does not support references, but it does support arrays, numbers, Boolean values, and errors. For more information about the Register function, see the Microsoft Excel Software Development Kit (SDK).

Method 3

When the cells contain text, use Automation to get the values from the cells. You can use the information in a reference XLOPER to build a Range object that you can pass to Microsoft Excel through Automation. When you do this, values in cells are returned to the DLL as a SAFEARRAY, which you can use to build an XLOPER array of values.

The 32-bit Generic Framework example for Microsoft Excel in the Microsoft Software Library implements this method. The method is integrated in the Microsoft Excel SDK framework; therefore, it's not necessary to change any code that uses the Excel() wrapper.

For additional information, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q152152
   TITLE     : SAMPLE: FRMWRK32.EXE: Updated Generic.xll Template for Excel

1. Add xlAuto.cpp, xlCoerce.cpp and Framewrk.c to the existing project and place framewrk.h and xlcoerce.h in the directory for the project.

2. Call InitFramework() from the xlAutoOpen.

3. Call QuitFramework() from the xlAutoClose.

4. Add "CheckInstance" to the exports section of the DEF file for the project.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Excel 97 for Windows. This problem was corrected in Microsoft Excel 97 SR-1.

For additional information about SR-1, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q172475
   TITLE     : OFF97: How to Obtain and Install MS Office 97 SR-1