Register COM interop

Navneet Rana

Hello to All,

This is my very first time building an application which requires registering COM interop. The output of this application should be a library so as to load it into a different XYZ application that has COM scripting ability.The problem I am facing is the application I built works fine on my machine that has Visual Studio 2012(checking Register COM interop) But when I try it on a different machine, it wont properly in the XYZ application.After a lot of research and trying installShield installer , I have concluded that maybe I am missing something in my code.I was under the impression, that just declaring COMvisible to true and GUID attribute is enough.But I am surely missing something about the interface.I will really appreciate is someone can help me with a step by step tutorial for the same.

Below is what I am doing currently.

1) create a class library project and add the following code:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Runtime.InteropServices;

using Ivi.Visa.Interop;

namespace UsbLibraryCls

{

[Guid("0FB610DE-C81E-491E-BCC5-D897CDFA7CFD")]

[ComVisible(true)]

[ClassInterface(ClassInterfaceType.AutoDual)]

public class ComUsb

{

ResourceManager rMgr = new ResourceManager();

FormattedIO488 src = new FormattedIO488();

object resources = null;

public string OutputResources()

{

resources = rMgr.FindRsrc("USB[0-9]*::?*");

string[] resource_list = (string[])resources;

string allResources = String.Join(";", resource_list);

return allResources;

}

Here I add the VISA COM 3.0 library as a reference.

2) Create a console application:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Runtime.InteropServices;

using UsbLibraryCls;

namespace UsbLibConsole

{

class Program

{

static void Main(string[] args)

{

ComUsb Usb = new ComUsb();

Usb.OutputResources();

}

3) Both the projects are have x86 platform. And I check mark for "Register COM interop"

4) The library loads into the registery and I load this into the XYZ library by calling its ProgID.

And it works fine.

But When I try this on a any other target machine without VS with the same configurations as my laptop that has VS, the library loads into the registery but when i load it into the XYZ application it does not work.

I load it on the target machine by using RegAsm "fullpath\abc.dll" /tlb: abc.tlb /codebase.

I can say I have almost tried all the solutions I could find online. But I am missing some important detail.

All I want is when I call the OutputResources() function from the XYZ application. It should return a string with all the USB devices connected to the machine.

The code is barely 10 lines but I have spent more than a week trying this.

I am waiting on delivery of Install Sheild so have not tried that yet. But I created the .msi package

using advanced installer and installed it on target machine and still wont work.

I really would appreciate if anyone could point out where I am going wrong.

Thanks!

5 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
Accepted answer
Well, the recommended way to create a COM server from C# is to create an interface and a co-class which implements it rather than just a class. See for example this MSDN link:

http://msdn.microsoft.com/en-us/library/aa645738(v=vs.71).aspx

So this would give you here:

namespace UsbLibraryCls
{
[Guid("...Generate a diffent GUID here...")]
public interface IComUsb
{
string OutputResources();
}

[Guid("0FB610DE-C81E-491E-BCC5-D897CDFA7CFD")]
[ClassInterface(ClassInterfaceType.None)]
public class ComUsb : IComUsb
{
ResourceManager rMgr = new ResourceManager();
FormattedIO488 src = new FormattedIO488();
object resources = null;

public string OutputResources()
{
resources = rMgr.FindRsrc("USB[0-9]*::?*");
string[] resource_list = (string[])resources;
string allResources = String.Join(";", resource_list);
return allResources;
}
}
}

There's no need to specify the ComVisible attribute as it's true by default anyway.

I'm not saying this will be any better than what you already have but it's worth a try.
Navneet Rana12y ago
I had it spelled wrong.
Thank you so much for you help :-)
Vulpes12y ago
Yes, you can include as many public methods (or properties) in the interface as you like and the class can then implement them.

So, we'd now have:

[Guid("...Generate a diffent GUID here...")]
public interface IComUsb
{
string OutputResources();
string OptputIdn();
}
Navneet Rana12y ago
Hello Vulpes,
This question is related to this post.
Is it that one interface can give only one output?

For instance I have another function under ComUsb class as follows:
public string OptputIdn()
{

resources = rMgr.FindRsrc("USB[0-9]*::?*");
string[] resource_list = (string[])resources;

for (int i = 0; i < resource_list.Length; i++)
{

src.IO = (IMessage)rMgr.Open(resource_list[i], AccessMode.NO_LOCK, 2000, null);
src.IO.Timeout = 2000;

}

string identification = String.Join(";", resource_list);
return identification;
}

Now Can I have OutputIdn() called from IComUsb or not?
Navneet Rana12y ago
Thank you for replying back.
I guess i was looking for just this.
I did try this b4 you replied but wanted a re-assurance.
Thank you so much.

It works just great!!!