PRB: Compiled In-Process Server Used Before IDE Server

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

SUMMARY

A request for an object provided by both a compiled OLE server dynamic-link library (DLL) and an instance of the OLE server running in the Visual Basic for Windows integrated design environment (IDE) is filled by the compiled DLL.

MORE INFORMATION

Generally, OLE automation clients receive objects from an instance of an OLE server running in the Visual Basic for Windows IDE before they receive objects from a compiled server. Visual Basic for Windows accomplishes this functionality by temporarily adding or modifying registry keys when an IDE server is started and then restoring the original settings when the server is stopped. This was done to make debugging of OLE servers as easy as possible. However, if a server has previously been compiled into an OLE DLL, then objects are provided from that compiled DLL before they are provided by a server running in the IDE.

The reason for this behavior is rooted in the search path OLE uses when attempting to create an object. This search path is listed below:

- Inprocess server of same bitness - 32-bit local server (for 16-bit clients under a Microsoft Win32 operating

                       system)

Servers running in the IDE are always out-of-process. When a request for an object is made, OLE encounters the previously compiled in-process server before it encounters the one running in the IDE, and so it creates the object from that DLL.

WORKAROUND

It is possible to test the execution of what will become an OLE DLL in the IDE when you have a previously compiled DLL. To accomplish this functionality temporarily unregister the previously compiled DLL using Regsvr32.exe. Then reregister the DLL by using Regsvr32.exe. For example:

Do the following to unregister the previously compiled DLL:

   regsvr32.exe -u DLLName.DLL

   regsvr32.exe DLLName.DLL

Steps to reproduce problem

1. Start an instance of the 32-bit edition of Visual Basic 4.0 for Windows.

2. Click Class Module on the Insert menu to add a class module to the project.

3. Change the following properties on the new class module to the following:

         Instancing: 2 - Creatable Multiuse
         Public:     True
   
   

4. Add the following code to the class module:

         Public Sub Test()
            MsgBox "In DLL"
         End Sub
   
   

5. Click Module on the Insert menu to insert a new code module.

6. Add the following code to the code module:

         Public Sub Main()
            'do nothing
         End Sub
   
   

7. Click Options on the Tools menu to open the Options dialog box. Switch to the Project tab and change the following settings:

         Startup Form:  Sub Main
         Project Name:  DLLandIDE
         Startmode:  OLE Server
   

8. Click "Make OLE DLL File..." on the File menu to create a compiled OLE DLL.

9. Click Options on the Tools menu to again open the Options dialog box. Switch to the Project tab and type in the name of the DLL generated in step 8 in the Compatible OLE Server text box.

10. Click "Make OLE DLL File..." to recompile the DLL.

11. Change the line of code in the Test subroutine contained in the class

        module from "In DLL" to "In IDE."
    

12. Press F5 or click Start on the Run menu to run the server in the IDE.

13. Start another instance of the 32-bit edition of Visual Basic for

        Windows, and add the following code in the Form_Click event to the
        default form, Form1:
    

           Private Sub Form_Click()
              Dim MyObj As Object
    
              Set MyObj = CreateObject("DLLandIDE.Class1")
              MyObj.Test
           End Sub
    
    

14. Step through the code in the client program and see that the text of

        the message box displayed by the Test method contains "In DLL" and not
        "In IDE."