Cannot get registration-free COM working from VBA

Question

UPDATE: After spending 20+ hours trying to get a simple example working, I have realized that this is not as simple as it seems. Articles like this reveal the "gotchas" - and this was written before Windows 7 (which handles manifests differently). I'm sticking with exposing .NET assemblies to VBA via VSTO.

I made a simple COM-Visible .NET assembly and am trying to call it from Excel VBA. If I "Register for COM Interop" during my .NET build, I can call it from VBA successfully.

Sub VBA()    
    Dim obj As Object
    Set obj = actCtx.CreateObject("ComTest.Main")
    MsgBox obj.Test() '<-- Displays "Hello"
End Sub

However, I want to do registration-free.

Updated per advise from Hans:

I unchecked Register for COM Interop, and set my app.Manifest to:

<?xml version="1.0" encoding="utf-8"?>
<asmv1:assembly 
  manifestVersion="1.0" 
  xmlns="urn:schemas-microsoft-com:asm.v1" 
  xmlns:asmv1="urn:schemas-microsoft-com:asm.v1"
  xmlns:asmv2="urn:schemas-microsoft-com:asm.v2" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

  <assemblyIdentity
    type="win32"
    version="1.0.0.0" 
    name="ComTest" 
    publicKeyToken="a36a7110110d7bd7" />

  <clrClass
      clsid="{975DC7E0-4596-4C42-9D0C-0601F86E3A1B}"
      progid="ComTest.Main"
      threadingModel="Both"
      name="ComTest.Main"
      runtimeVersion="v4.0.30319">
  </clrClass>

  <file name = "ComTest.dll"></file>   
</asmv1:assembly>

I created a dummy "client.manifest" like this:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<asmv1:assembly 
  manifestVersion="1.0" 
  xmlns="urn:schemas-microsoft-com:asm.v1" 
  xmlns:asmv1="urn:schemas-microsoft-com:asm.v1" 
  xmlns:asmv2="urn:schemas-microsoft-com:asm.v2" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

    manifestVersion="1.0" 
    xmlns="urn:schemas-microsoft-com:asm.v1" >
    <assemblyIdentity
        name="xxx"
        version="1.0.0.0" />
    <dependency>
        <dependentAssembly>
            <assemblyIdentity
                type="win32"
                name="ComTest" 
                version="1.0.0.0"
                publicKeyToken="a36a7110110d7bd7" />
        </dependentAssembly>            
    </dependency>
</asmv1:assembly>

I modified my VBA to use client.manifest when creating my object:

Sub VBA()    
    Dim actCtx As Object
    Set actCtx = CreateObject("Microsoft.Windows.ActCtx")
    actCtx.Manifest = "C:\Users\me\Desktop\COM Test\ComTest\ComTest\bin\Debug\client.manifest"

    Dim obj As Object
    Set obj = actCtx.CreateObject("ComTest.Main")  '<-- Fails here.
    MsgBox obj.Test()    
End Sub

It fails on CreateObject with the less-than helpful error Method 'CreateObject' of object 'IActCtx' failed.

sxstrace shows that it reads client.manifest and creates the Activation Context. Process Monitor shows that it accesses ComTest.dll and searches the Registry for class 975DC7E0-4596-4C42-9D0C-0601F86E3A1B.

What am I missing?

Here's the .NET Code:

<ComVisible(True)>
<Guid("EB6AA207-ECC7-413B-9A9B-9D142FF2701D")>
<InterfaceType(ComInterfaceType.InterfaceIsIDispatch)>
Public Interface IMain
    Function Test() As String
End Interface

<ComVisible(True)>
<Guid("975DC7E0-4596-4C42-9D0C-0601F86E3A1B")>
<ProgId("ComTest.Main")>
<ClassInterface(ClassInterfaceType.None)>
<ComDefaultInterface(GetType(IMain))>
Public Class Main
    Implements IMain
    Public Function Test() As String Implements IMain.Test
        Return "HELLO"
    End Function
End Class

I'm running 64-bit Windows 7.

Trying to do the exact same in Microsoft Access. I am not finding a solid solution to deploying it in a production environment as I cannot get it to register on other machines when trying to execute regasm via C#. I thought RegFree would be a great solution to resolve this. Did you by chance ever get this working? — Anthony Griggs
@AnthonyGriggs I don't think it's possible, but I've struggled with the same problem. You can, however, dynamically register the DLL using the technique I described here. — Erik A

user1610015 user1610015 · Accepted Answer · 2013-03-19T15:25:20

To use registration-free COM, both the server (the assembly) and the client need to be in the same folder. See:

http://msdn.microsoft.com/en-us/magazine/cc188708.aspx

Cannot get registration-free COM working from VBA

1 Answers