PRB: Dynamically Changing Buffering Mode Doesn't Work

• 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.

   =CURSORSETPROP('Buffering',THIS.ListIndex)

STATUS

This behavior is by design.