comaddin.Object does not work

Question

I am trying to make two Excel addins talk. the 1st addin can be seen by the 2nd via app.COMAddins collection, and I verified that the addin instance has the right ProgId. however, the Object property yields <undefined value>, therefore, I can not call methods on that addin.

what can I do to figure out what is wrong?

Answer 1

The way it needs to be done is :

your first add-in should initialize set the Object property to something. It can be done in IDTExtensibility2.OnConnection method. You will need to cast OnConnection's AddInInstance parameter to Office::COMAddin, then set the Object property.

Then, when your 2nd add-in accesses COMAddins collection, it would access already initialized Object property.

Answer 2

set the Object property to --What? anything you want?

I was under the impression that the Object property automatically references the underlying object (meaning the COMAddin). is that not true?

Answer 3

Sorry to disappoint - but that is not true.Think of a scenario when a COM Add-in does not want to expose itself to any external components - then it just does not set AddInInst.Object.

The AddInInst.Object property can be set to any object the add-in wishes to set it to. But most commontly the code in IDTExtensibility2.OnConnection does just AddInInst.Object = me.

Hope this helps.

Answer 4

I am able to set .object field but not able to use this thru any external program :( Can you point me to some example which exposes a class using .object and the .object class's function can be called from external code?? I have seen the example XML.Export.dll but thats not exposing any class, the .object property of this addin is always nothing.

I have even tried changing the .connect = ture, but nothing seems to help. It would be really great if you could help me with some sample addin and a sample external code . A simple hello world type example will do.

Thanks a ton,

Vibhore

Answer 5

You are probably hitting marshalling problems - remember you are going to get a reference to your class through COM, so COM interop rules start applying.

Registering a class that is defined as below should work.  Make sure you class is marked with ComVisible(true) and regasm'ed.

public interface IMyInterface
{
  void MyMehotd();
}

 [ClassInterface(ClassInterfaceType.None)]
 [ComVisible(true)]
public class MyClass : IMyInterface
{
}