Reference assembly in VBA without registering the assembly as a COM component.

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I have an application that uses VBA to interface with libraries written in .NET. The assemblies for these libraries is then registered as COM components. I am trying to get rid of the COM registration part. Essentially, I want the application to be able to function as long as the assembly is present, regardless of whether or not the assembly has been registered.

From what I can gather, it seems to be possible. I found some promising looking code samples here and here. From these, I have tried the following:

VB

Application.VBE.ActiveVBProject.References.AddFromFile "C:\SomeDirectory\SomeAssembly.dll"

and

VB

Dim VBAEditor As VBIDE.VBE
Dim VBProj As VBIDE.VBProject

Set VBAEditor = Application.VBE
Set VBProj = VBAEditor.ActiveVBProject

VBProj.References.AddFromFile "C:\SomeDirectory\SomeAssembly.dll"

Neither works. The first one tells me "Expecting a var name", while the second one complains that "Type identifier is invalid".

So, anyone know what I'm doing wrong?

Also, I'm VERY new to VBA; so, if possible, please keep the explanations simple.

Posted 16-Jan-12 21:05pm

BotCar

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Sergey Alexandrovich Kryukov 17-Jan-12 3:21am

Is there any particular reason for using VBA at all? Why not using VB.NET?
--SA

BotCar 17-Jan-12 3:37am

Don't ask me, I'm just the coding monkey that gets to fix stuff ;-)

To be honest, I'm not sure. The application was created by an external vendor before I joined the team I'm in now, so I know very little about the reasoning behind it. However, would VB.NET be able to run within a host application like VBA can?

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Jason Gleim · Accepted Answer · 2012-01-17T06:02:00

There are problems.... mostly related to security... when you try to mix & match VBA and .net code. The COM wrapper marshals all of this for you which is why it will work if it is registered. Also... I think that the AddFromFile method is looking for the RegisterCOMComponent entry point which doesn't exist in a straight .net assembly but does if the assembly has been marked for COM interop. (Try running regsvr32 on a regular .net assembly. You should get a message about the entry point missing)

You don't talk about what the host app is so it's hard to say if a pure .net solution would be available. If it is MS Office 2007 or higher, you can do everything (and more) in .NET using the Office components. Plus, it will fit into the security scheme. For example, if you code-sign the add-in, users will not get prompted for security warnings when trying to run the add-in.

A pure .net solution would also let you define interfaces and discover/load assemblies at runtime. Handy for swapping out some functional component while leaving the rest of the app the same.