FIX: Parameters Passed as Empty Placeholders Default to NULL (314849)


The information in this article applies to:

  • Microsoft Visual FoxPro for Windows 7.0
This article was previously published under Q314849

SYMPTOMS

When you pass a parameter as an empty placeholder to a COM object from Visual FoxPro (VFP) 7.0, the placeholder defaults to a value of NULL (rather than .F. as in earlier versions of VFP).

RESOLUTION

To resolve this problem, obtain the latest service pack for Visual FoxPro for Windows 7.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

316964 How to Obtain the Latest Visual FoxPro for Windows 7.0 Service Pack

STATUS

Microsoft has confirmed that this is a problem in Microsoft Visual FoxPro for Windows 7.0. This problem was first corrected in Visual FoxPro for Windows 7.0 Service Pack 1.

MORE INFORMATION

Steps to Reproduce Behavior

  1. Create a new folder on your hard disk.
  2. Copy the VFP 7.0 run-time files Vfp7r.dll and Vfp7enu.dll to the new folder. The version number of these files should be 9262.
  3. Paste the following code in a new program (.prg) file and then save the file in the folder that you created in step 1:
    CD JUSTPATH(SYS(16))
LOCAL lcDLLStr AS STRING, ;
	loMyDll AS OBJECT
CLEAR

TEXT TO lcDLLStr NOSHOW
DEFINE CLASS SERVER AS SESSION OLEPUBLIC
	PROCEDURE SomeMethod(p1, p2, p3)
	   	RETURN p2
	ENDPROC
ENDDEFINE
ENDTEXT

STRTOFILE(lcDLLStr, "DLLMAIN.PRG", 0)
CREATE PROJECT DLLMAIN NOWAIT
_VFP.ACTIVEPROJECT.FILES.ADD("DLLMAIN.PRG")
_VFP.ACTIVEPROJECT.BUILD('DLLMAIN',4)
_VFP.ACTIVEPROJECT.CLOSE

loMyDll = CREATEOBJECT("DLLMAIN.SERVER")
? "With params like loMyDll.SomeMethod(.F.,,.F.), P2 =",loMyDll.somemethod(.F.,,.F.)
RELEASE loMyDll
  4. Run the code.
The COM DLL that is created by the sample code returns NULL for the second parameter that it is passed. If you delete the run-time files from the folder (causing the COM DLL to use the VFP 7.0 SP1 versions of these files) and then rerun the sample code, the DLL will instead return .F. for the second parameter.
Modification Type:MajorLast Reviewed:2/18/2002
Keywords:kbbug kbCodeSnippet kbDSupport KB314849
©2002 Microsoft Corporation. All rights reserved.