FIX: Top Level Forms with Menus Allow Access to Datasession 0

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

SYMPTOMS

You have an application based on a top-level form, which runs several child forms that are called from a menu. One of these forms contains a grid. If the table or cursor that is the grid's RecordSource is closed and then another form is instantiated, the system datasession will be selected and Visual FoxPro will be placed in an unstable state.

STATUS

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

This bug was corrected in Visual Studio 6.0 Service Pack 3.

For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:

Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

Q194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

MORE INFORMATION

The system datasession is used by Visual FoxPro to open the Foxuser resource file, form and class library files, report files, and so forth. It should not be accessible to the user under any circumstances. If the system datasession becomes selected, closing tables in it will cause Visual FoxPro to produce errors or terminate.

Steps to Reproduce Behavior

1. Run the following code from a program (.PRG) file:




PUBLIC oGrid, oMain
   * Make Form2 - it must be an SCX.
   MODIFY FORM form2 NOWAIT
   = aselobj(xx,1)
   xx[1].ShowWindow = 1   && Make it In Top-Level
   KEYBOARD '{y}'
   Release window 'form designer - form2.scx'

   * Create a table and add some data
   CREATE TABLE TEMP(TEMP1 C(6), TEMP2 C(6))  
   INSERT INTO TEMP (TEMP1, TEMP2) ;
   VALUES ("FIELD1", "FIELD2")

   CLOSE DATA ALL && Clean Start, no open tables open to start.

   oMain = CREATEOBJECT('MAIN')  && Top-level form
   oMain.Show
   READ events
   WAIT window 'DataSession Number is: '+alltr(str(set('datasession')))
   * Let's avoid problems and go back to datasession 1
   SET DATASESSION TO  1
   CLOSE DATA ALL

   DEFINE CLASS grid1 AS form
       ShowWindow = 1
       Caption = "GRID1"
       Name = "GRID1"
       ADD OBJECT grid1 AS grid WITH ;
           ColumnCount = 2, ;
           Name = "Grid1"
   ENDDEFINE

   DEFINE CLASS main AS form
       ShowWindow = 2
       Caption = "Click on Grid Form menu item"
       Name = "MAIN"

       PROCEDURE Show
           LPARAMETERS nStyle
           DO MenuProc WITH thisform,.T.
       ENDPROC

       PROCEDURE queryunload
           Clear events
       ENDPROC
   ENDDEFINE

   PROC MenuProc
       LPARAMETERS oFormRef, getMenuName
      	DEFINE MENU MyMenu IN (oFormRef.name) BAR
   	DEFINE PAD Pad1 OF MyMenu PROMPT "Grid Form" COLOR SCHEME 3 ;
   	    KEY ALT+C, ""
   	ON SELECTION PAD Pad1 OF MyMenu ;
   	    DO Proc1
   	DEFINE PAD Pad2 OF MyMenu PROMPT "Form 2" COLOR SCHEME 3 ;
   	    KEY ALT+F, ""
   	ON SELECTION PAD Pad2 OF MyMenu ;
   	    DO Proc2
   	Activate MENU MyMenu NOWAIT
   ENDPROC

   PROCEDURE Proc1
       SELECT 0
       USE TEMP alias TEMP
       SELECT TEMP
       oGrid=create('grid1')
       oGrid.show
       oMain.Caption = 'Click on Form2 menu item'
   ENDPROC

   PROCEDURE Proc2
       SELECT TEMP
       USE
       oGrid.release
       DO form form2
       oMain.Caption = "Click on Close Box to close =====>"
   ENDPROC 

2. Click on the Grid Form menu pad.



3. Click on the Form 2 menu pad.



4. Click on the close box in the main form.



5. A WAIT WINDOW will be displayed with the current Datasession, which will be 0.

Additional query words:

Keywords : kbContainer kbCtrl kbVFp500abug kbVFp600 kbVFp600bug KbDBFDBC kbVS600sp3fix kbGrpFox kbDSupport
Version : WINDOWS:5.0,5.0a,6.0
Platform : WINDOWS
Issue type : kbbug