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Q131181: How to Manage the Exiting Process with QueryUnLoad Event

Article: Q131181
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbcode
Last Modified: 15-FEB-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
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SUMMARY
=======

When a user attempts to leave a form, you want to query the user to ensure that
they really want to leave the form. Using the QueryUnload event of a form, you
can ask the user, and then take appropriate action in response.

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

As described in the Help menu, the QueryUnload event occurs before the Destroy
event. The ReleaseType property is set prior to the QueryUnload event being
called. The QueryUnload event occurs when:

- The CLEAR WINDOWS, RELEASE WINDOWS, or QUIT command is executed in code.

- The user double-clicks the Control-menu box.

- The user chooses Close from the Control menu on a Form.

QueryUnload is where you should put your exit confirmation dialog box to verify
that the user really wants to leave. The QueryUnload event uses a related
property, the ReleaseType property, to indicate how the user is exiting. This is
a particularly useful for users choosing the Close option from the Control menu
on a form.

The following table summarizes the values for the ReleaseType property and
indicates when the QueryUnload event is called.

Action                 ReleaseType Value    QueryUnload Called?
---------------------------------------------------------------
QUIT                   2                    Yes
CLEAR WINDOWS          1                    Yes
RELEASE WINDOWS        1                    Yes
Click in Close Box     1                    Yes
RELEASE thisform       0                    No

Note that the QueryUnload event is not called when a RELEASE thisform command is
called. Therefore, if you are using the RELEASE thisform command as a means of
exiting a form, you won't be able to use the code example below in the
QueryUnload event; you'll need to use an alternate method to achieve the same
result.

Code Sample
-----------

The following code sample demonstrates how to use the QueryUnload event in a
form:

     *--------------------------------------------------------------*
     * Program: QUNLDTST - QueryUnload test code                    *
     * Purpose: Demonstrates trapping user exit from form.      *
     *--------------------------------------------------------------*
     cMessageTitle = 'Test'
     cMessageText  = 'Did you *really* mean to close this form?'
     nDialogType   = 4 + 32 + 256
     *  4   = Yes and No buttons
     *  32  = Question mark icon
     *  256 = Second button is default
     nAnswer = MESSAGEBOX(cMessageText, nDialogType, cMessageTitle)
     DO CASE
       CASE nAnswer = 6
         RELEASE THISFORM
       CASE nAnswer = 7
         NODEFAULT
     ENDCASE

The use of NODEFAULT in the DO CASE construction overrides the default action of
closing the form, in effect canceling the user's actions.

Additional query words: VFoxWin

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Keywords          : kbcode 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0

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