PRB: OLE Server Terminate Not Fired If Client Uses 'End'

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SYMPTOMS

An OLE Server with loaded forms does not unload when the client program terminates by using the End statement, even if the OLE server is programmed to unload its forms in the Terminate event.

CAUSE

When you use End to shut down an object application, the Terminate events of objects are NOT executed. (This is analogous to forms -- if you use End, the QueryUnload, Unload, and Terminate events of forms are NOT executed.)

RESOLUTION

This behavior occurs under Microsoft Windows 95, Microsoft Windows version 3.X, and Microsoft Windows for Workgroups version 3.11. It does not occur under Microsoft Windows NT.

Good programming uses the Terminate event of a class module to clean up and release dependent object references. This is true for client applications that create OLE objects as well. The Terminate, QueryUnload, or Unload events gracefully close down any objects or forms that were created or loaded during the session.

The End statement is convenient, but it does NOT go through the complete sequence of cleaning up after your application. You should use it cautiously and sparingly when developing applications.

A Visual Basic client can destroy the last instance of an OLE Server it creates by:

• Setting it to Nothing (the preferred method).
• Shutting down by unloading the last form (acceptable, but not as desirable).
• Ending the program by executing the End statement (this can cause problems).

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

1. Create a minimal OLE server and client application. If you need more information on how to do this, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q129801

      TITLE     : How to Create and Use a Minimal OLE Automation Server
   
   

2. In the OLE server application, add the following code to the Class1_Terminate event:

      Sub Class1_Terminate ()
         MsgBox "I exited normally."
      End Sub
   
   

3. Run the OLE server and minimize Visual Basic.

4. Load or create the minimal OLE Client. If you need more information on how to do this, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q129801

      TITLE     : How to Create and Use a Minimal OLE Automation Server
   
   

5. Add a command button (Command1) to Form1.

6. Add the following code to the Command1_Click event:

      Sub Command1_Click ()
         Dim X As Object
         Set X = CreateObject("Project1.Class1")
         End
      End Sub
   
   

7. Start the program by choosing Start from the Run menu or by pressing the F5 key.

8. Click the Command1 button. The OLE server is created, and the End statement executes. When this happens, the Terminate event is NOT fired on the OLE server object.

Example Resolution for Failure to Fire Terminate

Add the following statement before the End statement in step 6:

   Set X = Nothing