What is a valid COM structure for JACOB library?

Question

I'm using the JACOB (Java COM Bridge) library to call registered COM Objects from my Windows OS. It took me a while until I figured out how JACOB works and to set up everything. So my current problem is that:

ActiveXComponent comp = new ActiveXComponent("iTunes.Application");

for example works, my iTunes starts properly etc. If I want to call a self generated and registered COM Object written in C# JACOB responds the following error:

Exception in thread "main" com.jacob.com.ComFailException: Can't co-create object

That my iTunes started was an indicator for me that everything is set up right, I'm not sure why JACOB can't call my own .dll

Currently I'm using the Visual Studio 2015 on build register for COM interop function which worked pretty good in the past for me. The COM object looks as following:

[Guid("EAA4976A-45C3-4BC5-BC0B-E474F4C3C83F")]
public interface ComClass1Interface
{
}

[Guid("7BD20046-DF8C-44A6-8F6B-687FAA26FA71"), InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface ComClass1Events
{
}

[ComVisible(true)]
[Guid("0D53A3E8-E51A-49C7-944E-E72A2064F938"), ClassInterface(ClassInterfaceType.None), ComSourceInterfaces(typeof(ComClass1Events))]
[ProgId("test.Application")]
public class ComClass1 : ComClass1Interface
{
}

Is anything wrong with my C# dll or does JACOB require a certain type of structure in this dll?

Unfortunately I could not find any COM examples for JACOB.

Thanks in advance.

EDIT:

If i change my first line to:

ActiveXComponent comp = new ActiveXComponent("CLSID:{C9888A8E-8D23-4185-9D7D-A1E0B812803D}");

I'm getting following Exception:

Exception in thread "main" com.jacob.com.ComFailException: Can't find moniker

My .dll should be registered though.

score 1 · Answer 1 · answered Apr 14 '16 at 17:43

I would first write a VBS (VB script) program to test your DLL and make sure it runs.

set obj = CreateObject("test.application")
MsgBox TypeName(obj)

Make sure it succeeds. If it fails, then (assuming a 64-bit OS), try running it with c:\windows\syswow64\wscript.exe path\to\your\script.vbs.

Check to see whether your Java process is a 64-bit or 32-bit process. Your C# DLL has to be registered with the same bit-ness as your Java process for it to succeed.

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

Thanks for the hint, I was able to find a solution:

Visual Studio apparently registered my COM-Object as 32 bit. I'm not sure if this is a default setting(?).

So two simple steps to solve the problem:

open your windows cmd as admin.
Run the following Command:

C:\Windows\Microsoft.NET\Framework64\v4.0.30319\RegAsm.exe /verbose /nologo /codebase "path to your dll"

The command will register the .dll in 64 bit and not 32. This solved the problem for me and I could use it via JACOB.

What is a valid COM structure for JACOB library?

2 Answers2