Using C com object in C#

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I have followed this tutorial COM in plain C[^]
and created and registered a com object and now i need to use this com object in c#. i have tried TLBImp to generate a interop lib but getting error 'not a valid lib', i tried to register the .dll (Iexample.dll) using regsvr32 but then error came ' the DLLRegistryServer entry point is not found'.

now what should i do to be able to use it in my c# project.
i do not want to use P/Invoke and C++/CLI for this case.

Posted 19-Aug-15 21:19pm

RajneeshSaysHello

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CPallini 20-Aug-15 3:31am

If you cannot register your COM component, then it is broken. You have to fix it.

barneyman 20-Aug-15 4:42am

for the love of cheese, use ATL to create a COM object - trying to use flat C to provide an OOP solution is an exercise in frustration

F-ES Sitecore 20-Aug-15 5:41am

Having a scan of the article, the fact that it talks about manual registration makes me think the article doesn't explain how to make a "proper" COM DLL that is recognised as such. If you follow the article you shouldn't need to use regsvr32, the object should already be creatable. As long as the object is configured and works, all you have to do is reference it from Visual Studio (it will be listed in the COM objects list) and VS will create a .net interop dll.

Philippe Mori 20-Aug-15 8:41am

Why are you doing COM in plain C if you want to use those DLL from C#? It would be much simpler to write an assembly directly in C# or maybe in C++/CLI if you want to use some (existing) C/C++ code.

RajneeshSaysHello 21-Aug-15 7:30am

because i think com is faster than p/invoke and c++/cli

Philippe Mori 21-Aug-15 7:57am

You would work very hard and it is not even sure that you would gain any performance improvement.

If you already have C/C++ code or if you need to use some specific CPU instructions (for vectorized operations for example) for intensif processing, then C++/CLI route should probably be used (if P/Invoke does not give you enough control).

You really have to be sure that you actuall have any performance gain as this approach will have a significant impact on development time (more code to write and debug) and maintenance...

For most applications, you should use only C#... If C++ code make sense then C++/CLI bridge between C++ and C# is probably the best choice as you can write more optimized conversion code as you have direct access to both world and such bridge can also be optimized to batch changes for example if necessary.

For performance, use a profiler to make sure that you get significant performance gain. Otherwise, write maintainable code.

Philippe Mori 21-Aug-15 8:16am

In the past, I have wrote C++ code to be used from C# and I was thinking to have some performance gain but it was not really the case.

For best performance, it is usually best to have either a managed application only (C#) or a native one only (C++). When using both, there is some hidden overhead (probably native <--> managed transitions).

If performance is the reason, then you have to use a profiler to validate different approach. For sure C code would have to do intensive work so that performance gain would be greater than performance lost of interfacing C/C++ with C#. And performance gain has to be relevant. Gaining 1% gain on 1 ms operation called once when the user click a button is irrelevant.

2 solutions

Solution 3

See Introduction to COM - What It Is and How to Use It.[^] and its follow on article.

Posted 19-Aug-15 23:22pm

Richard MacCutchan

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Maciej Los 20-Aug-15 5:47am

Good idea!

RajneeshSaysHello 21-Aug-15 7:29am

thanks for the link

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Maciej Los · Accepted Answer · 2015-08-19T21:45:00

Solution 1

As CPallini[^] mentioned in the comment to the question, you have to fix it. Try this: How to use the Regsvr32 tool and troubleshoot Regsvr32 error messages - Common solutions for Regsvr32 errors[^].

This might be helpful in case of necessity of changes in COM component: Exposing native to managed - C++/CLI vs. P/Invoke[^]

Posted 19-Aug-15 21:45pm

Maciej Los

Comments

CPallini 20-Aug-15 3:56am

5.

Maciej Los 20-Aug-15 4:35am

Thank you, Carlo.