Can't instantiate a COM object written in C# from VBA (VB6 ok)

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Using VS 2008, here is my COM object

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace TestCom
{    
    [Guid("9E5E5FB2-219D-4ee7-AB27-E4DBED8E123E")]
    [ClassInterface(ClassInterfaceType.AutoDual)]
    [ProgId("Test9.COMINT")]
    public class TestComClass  
    { 
        public void Init(string userid, string password)
        {
            MessageBox.Show(string.Format("{0}/{1}", userid, password));
        }       
    }
}

If I build this and register it on a production machine as follows

REGASM /CODEBASE TESTCOM.DLL

From a simple VB6 app this works fine

Private Sub Form_Load()
  Dim o As Object
  Set o = CreateObject("Test9.COMINT")
  o.Init "A", "B" 
End Sub

This exact same code called from VBA in Excel gives

"automation error" (0x80131700)

Everything works fine on a development machine, just not on a production machine with just .NET and MS Office installed.

Update

I think this is something to do with the .NET framework not being initialized properly, when running under Excel. If I use Filemon I can see it skip around looking for MSCORWKS.DLL. When I call the same object from VBScript, it finds MSCorwks.dll fine.

When I called CorBindToCurrentRunTime from VBA to try to forcibly load the CLR, interestingly I get the exact same HRESULT (0x80131700) as when I do CreateObject() in VBA.

Therefore I think it is a framework initialization issue.

c#
.net
vba
com
com-interop
asked on Stack Overflow Dec 17, 2008 by (unknown user) • edited Oct 22, 2012 by bluish

5 Answers

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13
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I'm going to answer my own question, hopefully to spare others the hours of tedious drudgery I have just endured.

If you get this, it is because the .NET based COM assembly can't find the .NET framework

The solution is simple. Create a file containing the following

<?xml version="1.0"?>
<configuration>
  <startup>
   <supportedRuntime version="v2.0.50727"/>
  </startup>
</configuration>

Call it "Excel.Exe.Config" and place it in the same directory as "EXCEL.EXE"

Problem solved!

answered on Stack Overflow Dec 17, 2008 by (unknown user)
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installing the follow fix will resolve this issue http://www.microsoft.com/downloads/details.aspx?FamilyID=1b0bfb35-c252-43cc-8a2a-6a64d6ac4670&displaylang=en

answered on Stack Overflow Jul 8, 2010 by ryang
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RC1, I tested this with your code from VBScript and from within Office 2007's Excel, everything works fine.

Since your able to create the COM object from within a VB6 form we should assume that your .net framework is ok. Can you rule out issues with VBA? Can you create a .vbs file and put this in it:

Dim o As Object  
Set o = CreateObject("Test9.COMINT")  
o.Init "A", "B"

Save the file and double click it. If you get an error, then I would think there is an issue with it being registered, if you don't get an error, then I would look at Office and VBA and see if something is missing or not installed properly.

Another option is to add a reference to COM object and use early binding? I think you might need to export a typelibrary first, but you should be able to add a reference and simple new the object up.

answered on Stack Overflow Dec 17, 2008 by JoshBerke
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This works for me from VBA... I tried it using Word & Excel 2003 (SP3).

I'm not sure what you mean by "production" machine. Because this is a "client" application and must be executed on the client using Excel.

If you're automating Excel on the server and triggering this "interop" through a VBA call, you're asking for trouble :)

Assuming that by production, you mean the client machine where user will be using the Excel template / doc, these are the following pointers:

  1. Make sure you have the appropriate .Net framework
  2. That you have latest service packs for Office
  3. Try ascertain if this is a rights issue.

If you're feeling adventuristic, you could use a process explorer [from Microsoft sysinternals site] to see what're the DLLs loaded and where exactly are you getting the error and compare it to the list on your dev box.

Hope this helps.

answered on Stack Overflow Dec 17, 2008 by Vyas Bharghava
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rc1 is correct in that this is a .net error, thrown when Office can't decide which version of the Framework to use. However, Office isn't throwing a wobbly simply because it's spoilt for choice. There is a bug in how Office 2003 interacts with .net 2.0.

Installing the fix from Microsoft (KB908002) is a more flexible way of solving the problem than by forcing Excel to run in a particular version of .net.

See also: http://www.biopdf.com/guide/trouble_shoot_microsoft_office_2003.php

answered on Stack Overflow Aug 23, 2011 by Robino

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