How to create instance of Win32 COM object?

Question

How to create instance of Win32 COM object?

Leo Ayala 21

I have some legacy code that need to port over to C#. There is a COM server object written in C++ that is called by other Win32/MFC apps. I'm trying to see if I can write a C# app and create an instance of the COM object just like the other Win32/MFC apps. I referenced the Type Library (tlb) in my C# project but when I create an instance of the COM server object, I get the following error:

Creating an instance of the COM component with CLSID {723440AD-AB68-11D4-91F9-00A0CCE1FA84} from the IClassFactory failed due to the following error: 80010108 The object invoked has disconnected from its clients. (Exception from HRESULT: 0x80010108 (RPC_E_DISCONNECTED)).

The IDL is as follows:

import "oaidl.idl";
import "ocidl.idl";
[
    object,
    uuid(723440AC-AB68-11D4-91F9-00A0CCE1FA84),
    dual,
    helpstring("ITestServer Interface v2.2"),
    oleautomation,
    pointer_default(unique)
]
interface ITestServer : IDispatch
{
    /* many methods */
}

library MyTestServerLib
{
    importlib("stdole32.tlb");
    importlib("stdole2.tlb");

    coclass TestServer
    {
        [default] interface ITestServer;
    };
}

The legacy apps work fine on my PC so I know that the COM object is registered. It is only my C# app that fails. Any idea as to why I would be getting the error mentioned above?

Any help will be greatly appreciated.

Regards,
LA

RLWA32 52,566 Reputation points

2020-12-05T18:43:31.81+00:00

The posted IDL has omitted uuids for the library block MyTestServerLib and the coclass TestServer.. I don't know how the type library was created, but my copy of the MIDL compiler issues error MIDL2079 for such omissions.

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Your answer

RLWA32 52,566 Reputation points

2020-12-05T18:43:31.81+00:00

The posted IDL has omitted uuids for the library block MyTestServerLib and the coclass TestServer.. I don't know how the type library was created, but my copy of the MIDL compiler issues error MIDL2079 for such omissions.

Answer 1

Castorix31 91,871

I don't reference the .tlb

For example, with a COM interface IImgCtx (used to display pictures) =>

[ComImport]
[Guid("3050F3D7-98B5-11CF-BB82-00AA00BDCE0B")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IImgCtx
{
         // declare all methods...
}

then :

Guid CLSID_IImgCtx = new Guid("3050F3D6-98B5-11CF-BB82-00AA00BDCE0B");
Type ImgCtxType = Type.GetTypeFromCLSID(CLSID_IImgCtx, true);
IImgCtx pImgCtx = (IImgCtx)Activator.CreateInstance(ImgCtxType);

Leo Ayala 21

I tried as you suggested using GetTypeFromCLSID (and GetTypeFromProgID) but still didn't work.

import "oaidl.idl";
import "ocidl.idl";

    [
        object,
        uuid(723440AC-AB68-11D4-91F9-00A0CCE1FA84),
        dual,
        ...,
        oleautomation,
        pointer_default(unique)
    ]
    interface ITestServer : IDispatch
    {
        ...
    };

[
    uuid(723440A0-AB68-11D4-91F9-00A0CCE1FA84),
    ...,
    ...
]
library MyTestServerLib
{
    importlib("stdole32.tlb");
    importlib("stdole2.tlb");

    //forward decl
    dispinterface IEventUpdate;

    [
        uuid(723440AD-AB68-11D4-91F9-00A0CCE1FA84),
        ...
    ]
    coclass TestServer
    {
        [default] interface ITestServer;
        [default,source] dispinterface IEventUpdate;

    };

};

RLWA32 52,566 Reputation points

2020-12-05T19:40:05.193+00:00

Post the C# code you are using so that we can better understand the situation.
Leo Ayala 21 Reputation points

2020-12-05T21:30:51.32+00:00
The following is what I used as a test. Note that I had changed the interface and class names for the post. The ProgID below is the actual name as it appears in the registry. The COM object was created as a Win32 app but I'm running on a x64 PC. Hopefully that i s not a problem. The exception occurs on the call to Activator.CreateInstance.

try { //Guid CLSID_QServer = new Guid("723440AD-AB68-11D4-91F9-00A0CCE1FA84"); //Type ImgCtxType = Type.GetTypeFromCLSID(CLSID_QServer, true); Type ImgCtxType = Type.GetTypeFromProgID("QueueMGR.QServer", true); var pServer = Activator.CreateInstance(ImgCtxType); } catch(Exception ex) { Debug.WriteLine(ex.Message); }

Leo Ayala 21

Below is the code from one of the MFC apps that also connects to the same server.

BOOL CQConnect::ConnectToServer(IQServer **pServer,CString sServerName)
{
BOOL bRet = FALSE;
COSERVERINFO serverinfo;
COSERVERINFO* pServerInfo = NULL;

serverinfo.dwReserved1 = 0;
serverinfo.dwReserved2 = 0;
serverinfo.pwszName = sServerName.AllocSysString();
serverinfo.pAuthInfo = NULL;

if(!sServerName.IsEmpty())
    pServerInfo = &serverinfo;

MULTI_QI qi[] = {   { &IID_IQServer,NULL,0}, };

HRESULT hr = CoCreateInstanceEx(CLSID_QServer, NULL, CLSCTX_LOCAL_SERVER | CLSCTX_REMOTE_SERVER, pServerInfo, 1, qi);

if(SUCCEEDED(hr))
{
    if(SUCCEEDED(qi[0].hr))
    {
        *pServer = (IQServer *)qi[0].pItf;
        bRet = TRUE;
    }
    else
    {
        pServer = NULL;
    }
}

::SysFreeString(serverinfo.pwszName);
return bRet;

}

RLWA32 52,566 Reputation points

2020-12-07T10:34:53.35+00:00

So far, none of the information available gives me any substantive clue to why the out-of-process server has disconnected. Does the COM server terminate abnormally when this happens? Does it continue running?

Can you debug the COM server to see what is happening when the C# code attempts to instantiate the COM object?

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How to create instance of Win32 COM object?

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