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Q140653: PRB: Cursor-Based Grid Goes Blank If SQL SELECT Resets Cursor

Article: Q140653
Product(s): Microsoft FoxPro
Version(s): 3.00 | 3.00b
Operating System(s): 
Keyword(s): kbvfp300 kbvfp500 kbvfp600
Last Modified: 06-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 5.0, 5.0a, 6.0 
- Microsoft Visual FoxPro for Macintosh, version 3.0b 
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SYMPTOMS
========

If a grid's RecordSource property is set to a cursor, and then the SQL SELECT
command resets the cursor, the grid appears blank if the RecordSource property
is not set back to itself.

The following command will refresh the grid properly if a SQL SELECT is run to
rebuild the cursor, but if the grid's column or header properties have been
customized, these customized changes will be lost and the grid's column and
header properties will change back to their default settings:

     THISFORM.GRID1.RECORDSOURCE=THISFORM.GRID1.RECORDSOURCE

Such customization could be headers with different names, longer column lengths,
and code placed in the events of columns or headers. For more information,
please see the following article in the Microsoft Knowledge Base:

  Q131836 PRB: Grid Not Refreshing Displaying a Cursor from Query

CAUSE
=====

When you rebuild the cursor that the grid is based on with the SQL SELECT
command, the original cursor has to be destroyed before the new cursor can be
created. When this happens, the grid columns and headers are also cleared and
then recreated. Even when the grid's RecordSource is set back to itself, the
custom settings of the grid's columns and headers are lost.

RESOLUTION
==========

To refresh the grid without losing the custom properties of the columns and
headers, set the RecordSource property to a dummy cursor that already has been
created with the same fields as the cursor the grid is based on. After the SQL
SELECT is run, change the RecordSource property back to the rebuilt cursor. This
allows the properties of the columns and headers to remain intact while the
cursor is being rebuilt.

STATUS
======

This behavior is by design.

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

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

1. Open the Customer.dbf table located in the \Vfp\Samples\Data directory, and
  create a form called GridForm.

2. Place the following code in the Load event of the form:

     SELECT cust_id, city, country FROM customer INTO CURSOR Temp1
     SELECT cust_id, city, country FROM customer WHERE country = "" ;
        INTO CURSOR Temp2

3. Place the following code in the Destroy event of the form:

     SELECT Temp1
     USE
     SELECT Temp2
     USE

4. Place a grid on the form, and give the grid the following property settings:

     ColumnCount=3
     RecordSourceType=Alias
     RecordSource=Temp1

5. Change the caption of the grid1.Column1.header1 to Customer Id and the
  Column1 Width property to 100.

6. Add a text box to the form.

7. Add a command button, and place the following code in its Click event:

     THISFORM.GRID1.RECORDSOURCE = "Temp2"
     SELECT cust_id, city, country FROM customer ;
        WHERE country = Thisform.text1.value ;
        INTO CURSOR Temp1
     THISFORM.GRID1.RECORDSOURCE = "Temp1"

8. Run the Form. Type Spain in the text box, and then click the command button.
  The grid should display all records where the country field is equal to
  Spain. Note that the name of the header of column 1 stays the same and the
  width of the column doesn't change. By changing the RecordSource of the grid
  to the cursor called Temp2, the properties of the columns and headers are not
  reset when the Temp1 cursor is rebuilt.

9. Change the two THISFORM.GRID1.RECORDSOURCE lines in the Click event of the
  command button into comments and add the following as the last line of code:

     THISFORM.GRID1.RECORDSOURCE = THISFORM.GRID1.RECORDSOURCE

  After running the form, typing a country name in the text box, and clicking
  the command button, note that the column name changes and the width is
  smaller.

Additional query words: VFoxMac VFoxWin

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Keywords          : kbvfp300 kbvfp500 kbvfp600 
Technology        : kbHWMAC kbOSMAC kbVFPsearch kbAudDeveloper kbVFP300bMac kbVFP300 kbVFP500 kbVFP600 kbVFP500a
Version           : 3.00 | 3.00b

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