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Q221720: FIX: COM Servers Cannot Redimension Arrays Passed By Reference

Article: Q221720
Product(s): Microsoft FoxPro
Version(s): WINDOWS:5.0,5.0a,6.0
Operating System(s): 
Keyword(s): kbCOMt kbvfp500aBUG kbvfp600bug kbVS600sp3fix kbGrpDSFox kbDSupport
Last Modified: 14-SEP-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a, 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

You pass an array by reference to a method of a COM server built in Visual
FoxPro. The method redimensions the array. If you call the method from a Visual
FoxPro 6.0 client and use the COMARRAY function, you may see the following
error:

  OLE IDispatch exception code 302 from Visual FoxPro for Windows: Data type
  mismatch...

If you call the method from a Visual FoxPro 5.0 client, or a Visual FoxPro 6.0
client not using the COMARRAY function, you may not see an error, but instead
the array will not be redimensioned, and the array's original contents remain
unchanged. From clients other than Visual FoxPro, you may see the earlier
behaviors, or other variations.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

This bug has been fixed in Visual Studio 6.0 Service Pack 3.


MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Create a new project called Arraytest.

2. Add a new program to the project.

3. Paste the following code into the program:

     DEFINE CLASS arraydim AS CUSTOM OLEPUBLIC
        cVerStr = VERSION()
        PROCEDURE GetArray(taArray, tnRows)
           IF PARAMETERS() < 2
              tnRows = ALEN(taArray)
           ENDIF
           LOCAL lni
           DIMENSION taArray[tnRows]
           FOR lni = 1 TO ALEN(taArray)
              taArray[lni] = lni
           ENDFOR
           RETURN
        ENDPROC
     ENDDEFINE

4. Save the program as Arraytest.prg.

5. Build the project into a COM DLL.

6. Run the following code from a program (.prg) file:

     CLEAR
     CLEAR ALL
     LOCAL ARRAY laArray[5]
     LOCAL OX
     ox = CREATEOBJECT('arraytest.arraydim')
     * =COMARRAY(ox,11)
     STORE 'X' to laArray
     ?'Value of first element',laArray[1]
     ?'Array length before', ALEN(laArray)
     ox.GetArray(@laArray, 10)
     RELEASE ox
     ?'Array length after', ALEN(laArray)
     ?'Value of first element',laArray[1]

7. From a Visual FoxPro 5.0 client (this must be done with the COMARRAY function
  removed) the array length and value of the first element are unchanged. From
  a Visual FoxPro 6.0 client, using the COMARRAY function, the error listed in
  SYMPTOMS will occur. From a Visual FoxPro 6.0 client not using the COMARRAY
  function, the behavior is the same as that under Visual FoxPro 5.0.

REFERENCES
==========

Visual FoxPro Help, COMARRAY() topic.

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Jim
Saunders, Microsoft Corporation.


Additional query words:

======================================================================
Keywords          : kbCOMt kbvfp500aBUG kbvfp600bug kbVS600sp3fix kbGrpDSFox kbDSupport 
Technology        : kbVFPsearch kbAudDeveloper kbVFP500 kbVFP600 kbVFP500a
Version           : WINDOWS:5.0,5.0a,6.0
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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