Q248116: HOWTO: Use the Session Class to Provide a Private Data Session

Article: Q248116
Product(s): Microsoft FoxPro
Version(s): 6.0,6.0 SP3
Operating System(s): 
Keyword(s): kbOOP kbvfp600 kbVS600sp3 kbGrpDSFox kbDSupport kbCodeSnippet
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Studio 6.0 SP3 
- Microsoft Visual FoxPro for Windows, version 6.0 
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SUMMARY
=======

Visual Studio 6.0 Service Pack 3 added the Session Class to Visual FoxPro. This
class allows you to create a private data session without the use of a form. The
benefit to this is that it allows you to create a lightweight (in terms of
resource usage) custom object with encapsulated data. You previously would have
needed a form, with all its associated overhead, or an empty formset to do
this.

One of the best places to use this is in multithreaded DLLs (also added in
Service Pack 3) since resource usage is at a premium in most cases where you
would be using them.

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

An example of how to use this new class follows.

  DEFINE CLASS myPrivateDSClass AS session

  PROCEDURE UseTable
      *!* By using the table inside a method of the session object,
      *!* you are working in the object's DataSession.
      LPARAMETER tcTable
         
      IF NOT USED(tcTable)
          USE (tcTable) IN 0
      ENDif
  ENDproc

  PROCEDURE Destroy
      CLOSE DATA ALL
  ENDproc

To see this class in action, save the above code into MyDS.prg, and then run the
following code:

  CREATE TABLE myDSTest (cTest C(10))
  USE DBF() SHARED
  *!* CREATE TABLE makes an exclusively-used table. USE DBF() SHARED is
  *!* a good method for not having to remember the path to the table.
  FOR i = 1 TO 10
     INSERT INTO myDSTest ;
        VALUES (TRANSFORM(i))
  ENDfor

  oDS = NEWOBJECT("myPrivateDSClass", "MyDS.prg")    
  *!* NEWOBJECT allows you to specify a class in a program or other 
  *!* location without the use of SET CLASSLIB TO ... ADDITIVE.
  oDS.UseTable("myDSTest")
  SET

  WAIT WINDOW "Suspending... RESUME to remove Session Object." NOWAIT
  *!* The following line is needed to keep oDS in scope, so you can
  *!* see the datasession.
  SUSPEND

SET opens the Data Session window. If you switch between the default data session
and MyPrivateDS, you see myDSTest open in both, with the record pointer at the
top of one and the bottom of the other.

REFERENCES
==========

For more information, see the Session Object documentation in the MSDN Visual
FoxPro documentation, or "Additional Language Elements" in the Vfpsp3.chm file
which ships with Visual Studio 6.0 Service Pack 3.

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Garrett
Fitzgerald, Microsoft Corporation.


Additional query words: KBDSE

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Keywords          : kbOOP kbvfp600 kbVS600sp3 kbGrpDSFox kbDSupport kbCodeSnippet 
Technology        : kbVSsearch kbVFPsearch kbAudDeveloper kbVFP600 kbVS600SP3 kbVS600Search
Version           : :6.0,6.0 SP3
Issue type        : kbhowto

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