How to run COM server DLL as a surrogate process for integrating IM application with Office?

Question

How to run COM server DLL as a surrogate process for integrating IM application with Office?

Manoj 86

Hii, I am a beginner in Windows and Dotnet development and I am trying to integrate an IM client application with Office 2019.

I have made a COM server using .NET6.0 framework. I followed this documentation and the given sample as a reference to create and expose the COM server. I can see in the Registry that the class which has the attribute [ComVisible(true)] is registered. There are two entries in the registry:

1) Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Classes\ClassLibrary1.MyIMClient : which has the subkey "CLSID" and the corresponding class ID as its value.
2) Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{6E5C29C0-1196-4D6D-BC8E-BDA1604A4BF3} : which has the default value "CoreCLR COMHost Server" and two subkeys -

InProcServer32: which contains the path of the .comhost.dll file
ProgID: which contains the name of the class ClassLibrary1.MyIMClient

According to the official documentation, to discover the IM client application, Office looks for specific keys and entries in the Registry one of which is the ProcessName and if I see the existing keys which are being used for "Lync", they also contain ProcessId.

But my COM server is not running as a process, it is just a DLL file that was built from Visual Studio. So I read about this doc and followed the steps to use an "AppID" for the class. For now, I have taken the same AppID as the CLSID and I've left the DllSurrogate value as empty to use the system supplied surrogate. After all this, the COM server DLL is not running as a surrogate process. Can anyone please help me figure this out?

Thanks!
Manoj

RLWA32 49,536 Reputation points

2022-01-05T12:00:28.74+00:00

I'm not an Office expert but it seems to me that an IM client that supports integration with Office would not need you to supply a COM server.

Anyway, regarding COM --

The CLSID key also needs an AppID value (REG_SZ) for the guid of the AppID (same as the CLSID).

The process name of the system's COM surrogate is dllhost.exe. There may be more than one instance running at any time.
Manoj 86 Reputation points

2022-01-05T13:52:20.363+00:00

Thanks for replying @RLWA32 .

According to this doc - https://learn.microsoft.com/en-us/office/client-developer/shared/integrating-im-applications-with-office#setting-registry-keys-and-entries, the Office needs an IM client which provides a co-creatable class and implements the required interfaces. Along with this, they have also specifically mentioned that the Office connects as a client to the out-of-process COM server. So, I think that it is necessary to provide a COM server. If not, can you share any other way to integrate third-party IM applications with Office?

Regarding the AppID, I have already added the AppID value(REG_SZ which is the same as the CLSID) in all the CLSID keys. You can see the screenshot for reference.

The process name of the system's COM surrogate is dllhost.exe but it is not hosting the COM server made by me. I have confirmed that with the help of Process Explorer.
RLWA32 49,536 Reputation points

2022-01-05T14:15:32.257+00:00

What third party IM Client are you using and does it document that it supports office integration?

If you have properly configured your COM Server to be hosted in a surrogate process then you should be able to test by writing a minimal client application to instantiate a COM object from your server.
Manoj 86 Reputation points

2022-01-05T16:09:27.93+00:00

Right now, I have not added any third-party app related logic. I am creating an IM client application that will interact with the third-party app and provide presence information to Office.

How do I configure a COM server made in .Net to be hosted in a surrogate process?
RLWA32 49,536 Reputation points

2022-01-05T19:17:31.727+00:00

I used VS2019 and .Net 5 to create a COM Server. Then I wrote a minimal C++ COM client for the server. There were no issues using the COM Server as an in-process server. However, after I added the registry entries to load the server out of process using the system surrogate the CoCreateInstance function failed and returned E_NOINTERFACE. I realized that this was probably a marshaling problem. .Net 5 did not create a type library (I think .Net 6 does create them) so I manually created a type library and registered it to create the necessary entries for the standard marshaler. After this, the minimal COM client was able to use the .Net 5 COM Server out of process with the surrogate.

For example, the following process explorer image shows the surrogate and the loaded DLLs -

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RLWA32 49,536 Reputation points

2022-01-05T12:00:28.74+00:00

I'm not an Office expert but it seems to me that an IM client that supports integration with Office would not need you to supply a COM server.

Anyway, regarding COM --

The CLSID key also needs an AppID value (REG_SZ) for the guid of the AppID (same as the CLSID).

The process name of the system's COM surrogate is dllhost.exe. There may be more than one instance running at any time.
Manoj 86 Reputation points

2022-01-05T13:52:20.363+00:00

Thanks for replying @RLWA32 .

According to this doc - https://learn.microsoft.com/en-us/office/client-developer/shared/integrating-im-applications-with-office#setting-registry-keys-and-entries, the Office needs an IM client which provides a co-creatable class and implements the required interfaces. Along with this, they have also specifically mentioned that the Office connects as a client to the out-of-process COM server. So, I think that it is necessary to provide a COM server. If not, can you share any other way to integrate third-party IM applications with Office?

Regarding the AppID, I have already added the AppID value(REG_SZ which is the same as the CLSID) in all the CLSID keys. You can see the screenshot for reference.

The process name of the system's COM surrogate is dllhost.exe but it is not hosting the COM server made by me. I have confirmed that with the help of Process Explorer.
RLWA32 49,536 Reputation points

2022-01-05T14:15:32.257+00:00

What third party IM Client are you using and does it document that it supports office integration?

If you have properly configured your COM Server to be hosted in a surrogate process then you should be able to test by writing a minimal client application to instantiate a COM object from your server.
Manoj 86 Reputation points

2022-01-05T16:09:27.93+00:00

Right now, I have not added any third-party app related logic. I am creating an IM client application that will interact with the third-party app and provide presence information to Office.

How do I configure a COM server made in .Net to be hosted in a surrogate process?
RLWA32 49,536 Reputation points

2022-01-05T19:17:31.727+00:00

I used VS2019 and .Net 5 to create a COM Server. Then I wrote a minimal C++ COM client for the server. There were no issues using the COM Server as an in-process server. However, after I added the registry entries to load the server out of process using the system surrogate the CoCreateInstance function failed and returned E_NOINTERFACE. I realized that this was probably a marshaling problem. .Net 5 did not create a type library (I think .Net 6 does create them) so I manually created a type library and registered it to create the necessary entries for the standard marshaler. After this, the minimal COM client was able to use the .Net 5 COM Server out of process with the surrogate.

For example, the following process explorer image shows the surrogate and the loaded DLLs -

Answer 1

RLWA32 49,536

As I demonstrated in my earlier comment a properly configured .NET COM Server can be hosted in a surrogate process.

In addition to creating the necessary registry entries under AppID and CLSID you also need to create the registry entries needed for marshaling. This can be accomplished by registering a type library for you server.

Manoj 86 Reputation points

2022-01-07T08:50:01.307+00:00

Thank you for the answer @RLWA32 . I'll accept this answer as soon as I'm successful in doing this. It seems there are some problems with my COM server and I am still exploring them. As I said earlier, I am a beginner in .NET and Windows development. It would be really helpful if you could share a sample of a COM server made in .NET.

Thanks
Manoj

RLWA32 49,536

Following is a minimal .Net 5 COM Server that I have used in a surrogate process.

using System;
using System.Runtime.InteropServices;

namespace RLWAComServer
{
    [ComVisible(true)]
    [Guid("096F1988-E2E4-431D-B688-3D9A30D3716D")]
    [InterfaceType(ComInterfaceType.InterfaceIsDual)]
    public interface IServer
    {
        [DispId(1)]
        int Adder(int a, int b);
        [DispId(2)]
        int Subber(int a, int b);
    }

    [ComVisible(true)]
    [ClassInterface(ClassInterfaceType.None)]
    [Guid("3213E321-D3DF-4581-B546-257EB643377C")]
    public class Server : IServer
    {
        public Server()
        {
        }

        public int Adder(int a, int b)
        {
            return a + b;
        }
        public int Subber(int a, int b)
        {
            return a - b;
        }
    }
}

RLWA32 49,536 Reputation points

2022-01-08T01:12:15.22+00:00

There is a comprehensive sample that will create .Net COM servers (including using a surrogate) at https://github.com/dotnet/samples/tree/main/core/extensions/OutOfProcCOM

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How to run COM server DLL as a surrogate process for integrating IM application with Office?

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