PRB: Dynamically Changing Buffering Mode Doesn't Work

ID: Q133016

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 3.0

SYMPTOMS

Dynamically changing the BufferModeOverride property of the Data environment changes the property, but not the behavior of the buffering. A dialog box reporting "Property setting will not take effect until data environment reloaded" also appears.

CAUSE

Visual FoxPro does not change the behavior of the BufferModeOverride property dynamically while the tables are open. However, you can resolve the issue by closing the tables with the CloseTables method. Then change the property, and then open the tables again with the OpenTables method. The new setting of the buffering will then take effect.

RESOLUTION

The following steps show you how to create a form that contains a combo box that allows you to change the BufferModeOverride property dynamically.

1. Create a new form. Set the DataSession property to 2 and the Caption

   property to Customer. In the ACTIVATE method of the form, enter the
   following code:

   THISFORM.Refresh

2. Using the right mouse button, click the form, and choose Data

   Environment. Then Using the right mouse button again, click the Data
   Environment window, and choose Add.

   Add the CUSTOMER.DBF table located in the C:\VFP\SAMPLES\DATA or
   equivalent directory. Drag the first three fields in this table
   (Cust_Id, Company and Contact) onto the form.

3. Create a combo box and set the RowSourceType property to 1. Enter the

   following value into the RowSource property:  "1- Use Form Setting,2 -
   Pessimistic Row,3 - Optimistic Row,4 - Pessimistic Table,5 - Optimistic
   Table"

4. In the Valid method of the combo box, enter this code:

      THISFORM.Dataenvironment.CloseTables
      THISFORM.Dataenvironment.Cursor1.BufferModeOverride = THIS.ListIndex
      THISFORM.Dataenvironment.OpenTables

   In the Init method of the combo box, enter this code:

      THIS.ListIndex=1

5. Add a command button to the form, and enter Next in the Caption

   property. Enter the following code in the Click method:

   SKIP
   THISFORM.Refresh

6. Add another command button with Previous as the Caption with the

   following code in the Click method:

   SKIP - 1
   THISFORM.Refresh

7. Add another command button with Exit as the Caption, and enter the

   following code in the Click method:

   RELEASE THISFORM

8. Add a final command button with Write as the Caption, and enter the

   following code in the Click method:

   IF TABLEUPDATE(.T.,.F.)
      =MESSAGEBOX("SUCCESS",64)
   ELSE
      nAnswer=MESSAGEBOX("FAILURE - Write this New data ?",52)
      IF nAnswer=6
         =TABLEUPDATE(.T.,.T.)
      ELSE
         =TABLEREVERT(.T.)
         THISFORM.Refresh
      ENDIF
   ENDIF

9. Save the form, and create two instances of the form. You can now change

   the buffering dynamically with the combo box.

NOTE: Instead of changing the BufferModeOverride property, you can use the CURSORSETPROP() function to do the same thing. This method does not require you to open and close the tables. To use Table Buffering, ensure that MULTILOCKS is set ON. Below is a code example using the CURSORSETPROP() function:

   =CURSORSETPROP('Buffering',THIS.ListIndex)

STATUS

This behavior is by design.

Additional reference words: 3.00 VFoxWin KBCategory: kbprg kbprb kbcode KBSubcategory: FxprgMultiuser