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Q131560: BUG: Creating a Header Class Definition in a VCX Causes Error

Article: Q131560
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b
Operating System(s): 
Keyword(s): kbvfp kbvfp300bBUGkbbuglist
Last Modified: 15-FEB-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b 
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SYMPTOMS
========

When a visual class library (VCX) is edited programmatically and the VCX is
opened with the MODIFY CLASS command, Visual FoxPro is halted and an exception
error is generated.

CAUSE
=====

The Exception error is the result of a programming error. The information placed
in the VCX under program control is erroneous. In particular, creating a Header
or a Column class as a visual class yields this error because it is not possible
to create these classes in a VCX.

RESOLUTION
==========

Ensure that you are creating classes that are allowed in a visual class library.
Visual classes that cannot be created in a VCX require a container to exist.
They include:

- Column class

- Header class

- Page class

- Separator class

- OptionButton class

- DataEnvironment class

- Cursor class

- Relation class

You can however subclass all of these classes under program control.

STATUS
======

Microsoft has confirmed the fact that the product halts to be a problem in the
Microsoft products listed at the beginning of this article. We are researching
this problem and will post new information here in the Microsoft Knowledge Base
as it becomes available.

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

Steps to Reproduce Problem
--------------------------

The following program duplicates the Exception error. Please exercise caution if
you decide to run this sample program because it causes FoxPro to halt. This
code is provided as an illustration only. The comments highlight the source of
the error.

     CREATE CLASS grid1 OF myvcx AS Grid &&Set the ColumnCount property to 1
     USE myvcx.vcx
     LOCATE FOR baseclass = 'header'
     COPY TO myvcx2 NEXT 1
     APPEND FROM myvcx2
     GO BOTTOM
     REPLACE objname with 'myheader'\ 

  * The replace statement below is the cause of the error
  * A header object is created, and this is illegal in a VCX.

     REPLACE properties WITH STRTRAN(properties,"header1","myheader")
     REPLACE reserved1 WITH 'Class'
     REPLACE parent WITH SPACE(0)
     REPLACE UniqueID WITH LEFT(UniqueID,LEN(UniqueID)-1) + ;
        IIF(RIGHT(UniqueID,1)='Z','Q','Z')
     USE
     ERASE myvcx2.DBF
     ERASE myvcx2.FPT
     MODIFY CLASS myheader OF myvcx
     * choose the class MyHeader and click Open

Additional query words: crash hang

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Keywords          : kbvfp kbvfp300bBUG kbbuglist
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b
Version           : WINDOWS:3.0,3.0b

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