Comments on Moserware: Finally Understanding COM After Changing a Light B...

very nice post! After reading your post, I actuall...

2011-10-05T18:27:32.591-04:00

very nice post! After reading your post, I actually feel I understand COM better. (When I read many other COM articles, I felt more and more confused, just like stuck in mud.)

Simply amazing. I am glad clicked your link!!

2011-03-13T10:18:16.125-04:00

Simply amazing. I am glad clicked your link!!

Thanks for the article. It helped a lot. A few t...

2011-03-04T23:31:06.741-05:00

Thanks for the article. It helped a lot.

A few things that have showed up since you wrote it:

If the com object doesn't compile with Visual Studio 2008, try upgrading to SP1. This will fix the "incremental linker" error.

If you're using 64-bit Windows 7, and the C# code can't find your lightbulb object, set the build from "all platforms" to "x86".

I don't think COM's going away, but with the easy tools and the great tutorial, it's not so bad...

Great Article. Just a comment regarding: &quo...

2010-10-07T20:15:38.727-04:00
Great Article.

Just a comment regarding: "For example, different C++ compilers mangle function names differently."

To help clarify by anyone else who was confused by this statement. The compiler produces a "C" function with the standard underscore within the DLL. If you use bindump you will see a helper function to create the COM class. This helper function returns a pointer to the newly created class. Every function in a COM class must be declared virtual. Thus rather than knowing the address of every function it only needs to know the field that contains the function pointer.

However, I still have my reservations about this being compatible across compilers as not every compiler stores their fields on the same byte alignment.

Great article. Thank you for sharing!

2010-10-07T19:17:53.489-04:00
This comment has been removed by the author.

this is really helping me, when i read Don Box'...

2010-09-20T11:56:40.659-04:00
this is really helping me, when i read Don Box's book.. i felt like i was walking alone in the no-end tunnel, hair-pulling!

Great article, it's really useful with me, tha...

2010-06-30T02:46:27.571-04:00
Great article, it's really useful with me, thanks so much...

s: You might find this blog post helpful.

hi, I think it would be nice if you complete the p...

2009-11-17T02:58:19.655-05:00
hi, I think it would be nice if you complete the picture -put in class factory and map out the jargon.
I read this blog and a few other links -there is more jargon out there.
It looks like there is a class factory, then a com class which manages multiple COM interfaces. Not sure whether a COM component is the class object or the interface instance object

Victor Cheung: Thanks for pointing out the ...

2009-08-25T22:06:25.791-04:00
Victor Cheung: Thanks for pointing out the bad picture. I recreated the project and redid the final C# picture. Does it work for you now?

Hi,Jeff It seems there's something wrong wit...

2009-08-24T09:43:02.594-04:00
Hi,Jeff
It seems there's something wrong with the picture in this article.I have try 3 browsers: IE,google chrome,firefox, but no use. Can you help to fix this ,thanks

Dimitris: Are you referring to the layout of a COM object?

What are your thoughts about COM vs. .NET with respect to multiple platforms (e.g. Silverlight on non-x86 processors?) It seems that the VM/.IL approach gives .NET a long-term advantage.

Nice article. However like most other COM articles...

2009-06-11T09:42:49.749-04:00
Nice article. However like most other COM articles I have read, you didn't emphasize enough the most important aspect of COM which is binary compatibility. It is what enables true binary reusability across vastly different languages and runtimes.

I am also a firm believer that COM may actualy out live its replacement! .Net offers compeling productivity features and binary reusability, though it is fundumentaly constrained by its VM architecture while COM is far more versatile.

Dimitris

Kyle McIntyre: Good question. One example might be...

2009-02-14T09:19:00.000-05:00
Kyle McIntyre: Good question. One example might be if the component is coming from another vendor who only offers it as a COM dll.

It's a way to guarantee that you won't have to worry about getting the wrong version of a component and not have to modify the registry.

I'm no COM expert as I mention in the article, but it seems like a decent technology to share native components (as indicated by its heavy use by Windows and other Microsoft products). Registration free COM seems like a way to still use the components but without the registry ills.

Thanks for the great article. One question I have ...

2009-02-13T13:39:00.000-05:00
Thanks for the great article. One question I have for you is why would you ever want to use a registration-free com? If the class is only used by your application, shouldn't it just be built in to your application or at the most be a library that's linked in? I'm definitely a newbie at this, but it doesn't make sense to me to create a "com" when there's no communication involved.

Thanks,
Kyle

Huseyin: thanks for the nice comments on the artic...

2008-02-12T07:38:00.000-05:00
Huseyin: thanks for the nice comments on the article and blog as well as the links.

The icons were just Office 2007 avatar clipart I found while using PowerPoint 2007. The license agreement says that personal, non commercial use is permitted. So I assumed that they'd be a good fit for the post.

Great article about COM, a bare minimum for any Wi...

2008-02-12T04:28:00.000-05:00
Great article about COM, a bare minimum for any Windows programmer. (and btw great blog, starting to read your previous posts)

I was a VB6 programmer that didn't bother with the internals of COM and then it comes .NET and COM interop I have decided to learn how it works. Currently I am reading Adam Nathan's great .NET and COM: The Complete Interoperability Guide book, a must read for who are messing with CCWs and RCWs in a daily basis like me.

I also have a few COM related links here on my del.icio.us like Minimal COM object registration, What registry entries are needed to register a COM object

A little off-topic but the three icons in the blog post are awesome, is that a free collection which I can find on internet?

Mike: good catch! I didn't mention IDL since ATL h...

2008-01-31T19:52:00.000-05:00
Mike: good catch! I didn't mention IDL since ATL hides it so well. I added a bullet on that. I don't think I'm brave enough to go into MIDL on my own (and I haven't had to yet).

ATL is really nice as long as you don't have to dig too deep into the details :)

For true COM Zen, learn IDL. Develop typelibs sep...

2008-01-31T13:15:00.000-05:00
For true COM Zen, learn IDL. Develop typelibs seperately, compile with MIDL. When creating a COM component think in terms of implementing interfaces. Know the difference between C/C++ only COM and OLEAutomation compatible COM.
Remember as Don Box said:
1. COM is love
2. IDL is the lingua franca of COM.

undees: Interesting use of the metaphor :)

2008-01-30T09:01:00.000-05:00
undees: Interesting use of the metaphor :)

grnemo: Thanks for the kind words! Glad you liked ...

2008-01-30T08:59:00.000-05:00
grnemo: Thanks for the kind words! Glad you liked it.

Man, You are simply great!!!! This is a state of t...

2008-01-30T08:44:00.000-05:00
Man, You are simply great!!!! This is a state of the art article.

Thank you.

This is indeed a well-written article: it explains...

2008-01-29T15:46:00.000-05:00
This is indeed a well-written article: it explains why things are the way they are in COM.

However, it's also a beautiful reminder of why I hate COM. Imagine that the clerk at the auto parts store is surly and uncooperative, you have to fill out a ten-page form to get the light bulb, there's nothing in the box when you open it, and so on.

Colin and Pranav:

Thanks for the generous a...

2008-01-29T07:13:00.000-05:00
Colin and Pranav:

Thanks for the generous and encouraging feedback! I updated the article to fix the last bullet point and added more information about IDispatch.

Please let me know if there's anything significant about COM that I missed that beginners should know about.

Thanks again! Keep the feedback coming :)

Very well written article and extremely helpful. I...

2008-01-29T04:22:00.000-05:00
Very well written article and extremely helpful. I've been dabbling with the Win32 api for a while just for fun, and found a serious lack of good articles like yours. You should continue writing more such stuff.

Comments on Moserware: Finally Understanding COM After Changing a Light B...

very nice post! After reading your post, I actuall...

Simply amazing. I am glad clicked your link!!

Thanks for the article. It helped a lot. A few t...

Great Article. Just a comment regarding: &quo...

this is really helping me, when i read Don Box'...

Great article, it's really useful with me, tha...

s: You might find this blog post helpful.

hi, I think it would be nice if you complete the p...

Victor Cheung: Thanks for pointing out the ...

Hi,Jeff It seems there's something wrong wit...

Dimitris: Are you referring to the layout of a COM object? What are your thoughts about COM vs. .NET with respect to multiple platforms (e.g. Silverlight on non-x86 processors?) It seems that the VM/.IL approach gives .NET a long-term advantage.

Nice article. However like most other COM articles...

Kyle McIntyre: Good question. One example might be...

Thanks for the great article. One question I have ...

Huseyin: thanks for the nice comments on the artic...

Great article about COM, a bare minimum for any Wi...

Mike: good catch! I didn't mention IDL since ATL h...

For true COM Zen, learn IDL. Develop typelibs sep...

undees: Interesting use of the metaphor :)

grnemo: Thanks for the kind words! Glad you liked ...

Man, You are simply great!!!! This is a state of t...

This is indeed a well-written article: it explains...

Colin and Pranav:Thanks for the generous a...

Very well written article and extremely helpful. I...

Dimitris: Are you referring to the layout of a COM object?

What are your thoughts about COM vs. .NET with respect to multiple platforms (e.g. Silverlight on non-x86 processors?) It seems that the VM/.IL approach gives .NET a long-term advantage.

Colin and Pranav:

Thanks for the generous a...