BUG: Interface methods in the VBA Extensibility Library (VBE) are changed (269116)

SYMPTOMS

An out-of-process Automation client that early binds to the Visual Basic for Applications Extensibility 5.0 Library (VBEEXT1.OLB) of Microsoft Office 97 may receive the following error message when an Office 2000 application (or another VBA 6.0 host) is installed on the system:

In Visual Basic:

Run-time error 430:
Class does not support Automation or does not support expected interface.

In Visual C++:

0x80004002 (-2147467262)
E_NOINTERFACE: No such interface supported.

The error message only occurs when the system in question has an Office 2000 application (or VBA6 host application) installed, but the automation server is still an Office 97 (VBA5) application. If the application being automated is upgraded to Office 2000 (VBA6), the client application works normally without changes.

CAUSE

Microsoft Office 2000 ships with version 5.3 of the Visual Basic for Applications Extensibility Library (VBE6EXT.OLB). This library contains the type information for both the VBA5 (Office 97) and VBA6 (Office 2000) extensibility object model, and is designed for backward compatibility. Because the library shares the same library ID (LIBID) as version 5.0, it effectively acts as a replacement for the older type library. Under normal circumstances this would be fine because the library was designed for backwards compatibility.

However, the root (VBE) object did not change between versions and was not updated with a new interface for VBA6. But many of the objects accessed from that object did change and the methods of VBE now point to the new interfaces (with new IIDs) instead of the old ones. Because VBA uses the universal marshaller to remote its interfaces, this mistake can cause Component Object Model (COM) to incorrectly ask the server application for the new (VBA6) interfaces when constructing the proxy/stubs. Because older VBA5 servers do not support these interfaces, they report an error during this construction, and COM reports the error to the client in the preceding manner.

Re-registering the old type library (VBEEXT1.OLB) over the new one (VBE6EXT.OLB) resolves the issue for clients communicating with Office 97 (VBA5) servers, but could result in application errors or faults for new clients that early bind to Office 2000 (VBA6). Microsoft does not recommend this solution.

MORE INFORMATION

To reproduce the problem you need two computers, one with Microsoft Word 97 and VB6, and another with Word 97 and any other Microsoft Office 2000 application (except Word 2000).

Steps to Reproduce Behavior

On a computer with Word 97 and Microsoft Visual Basic 6.0, start Visual Basic and create a new Standard EXE project. Form1 is created by default.
On the Project menu, click to select References, and then add references to both the Microsoft Word 8.0 Object Library and the Microsoft Visual Basic for Applications Extensibility (5.0 Library).

Add a new Command button to Form1, and then place the following code in the code section:

Private Sub Command1_Click()
    Dim oWord As Word.Application
    Dim oDoc As Word.Document
    
    Dim oVBE As VBIDE.VBE
    Dim oVBProjs As VBIDE.VBProjects
    
    Set oWord = CreateObject("Word.Application")
    oWord.Visible = True
    Set oDoc = oWord.Documents.Add
    
    Set oVBE = oWord.VBE
    Set oVBProjs = oVBE.VBProjects
    
    MsgBox "Count of projects = " & oVBProjs.Count
    
    Set oVBProjs = Nothing
    Set oVBE = Nothing
    
    oDoc.Saved = True
    oDoc.Close
    Set oDoc = Nothing
    
    oWord.Quit
    Set oWord = Nothing  
End Sub

Compile the program to an executable and run the program. Note that the code runs and a message box appears with the count of loaded VBA projects that are running. Click OK to close Word.
Transfer the compiled application to another computer with Word 97 installed, and any other Office 2000 application (except Word 2000).
Run the executable, and note that you get a run-time error noting that the object does not support the expected interface.
To fix the problem, change the declaration for VBE to be late bound, as follows:
```
   Dim oVBE As Object
					
```
Recompile and distribute the application. It should run and report the number of loaded projects as expected.