How to create a dll based on the c code in vc++?

Karthik Agarwal

14y3.2k

Hi,

I have a C code for which i have to generate dll but i myself chose to do it in vc++ (visual studio 2008). I thought i have succeeded in doing that but i wasn't. I found that when i wrote a test application to refer that dll. when i tried to add a reference in test application it says that "could not add a reference to the file chosen because it is neither a .Net assembly or registered ActiveX control".

Can anyone tell me what's the problem or is this the way to do or else did i do something wrong? Earliest response is appreciated.

5 Replies

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Vulpes14y ago
Accepted answer
OK, so you're wanting to create an unmanaged C dll.

I'd follow the instructions in this article to create the dll:

http://www.codeproject.com/Articles/9826/How-to-create-a-DLL-library-in-C-and-then-use-it-w

To use it from VBA, you'll then need to include Declare statements for each C function you need to call. You're probably familiar with this already (similar to DllImport in C# or VB.NET) but, if you're not, this link should help:

http://msdn.microsoft.com/en-us/library/aa165080(office.10).aspx
Sam Hobbs14y ago
Attached is a C DLL project. I created it by using the default for not creating an empty project. I did however check the checkbox for creating a project that exports symbols. I then renamed the cpp files to c files and I removed the class that was in the generated code. Then I added a call to MessageBox. Then I created a C# program (not supplied) that tested the DLL and it works.

One useful thing that the code generated this way has is the macro that simplifies use of __declspec(dllexport) / __declspec(dllimport).

I suggest creating your C DLL project by generating a new project in the manner I describe instead of using that CodeProject article written by someone that did not yet have a lot of experience. Many developers, including myself, write articles about subjects we have just finished spending time learning but for this you can benefit from the immense experience of Microsft developers by using Visual Studio to generate a starter project.
Sam Hobbs14y ago
You cannot use CLR with C. That is impossible. So the only option is to create a native DLL. As has been established in previous replies here, you must use platform invoke (DllImport) to call a native DLL.

I suggest starting by generating a DLL project using Visual Studio. It does a good job of generating a skeleton DLL project. You will need to conver the code to C from C++ but that should be easy to do.
Karthik Agarwal14y ago
vulpes i want to use C code and then create a dll this is what is i know.
And regarding /clr i am using clr only if that's not correct i can change that to /clr pure.

To make to more clear about what my application is, i want to create a dll with the C code i have using any way and finally i want to use that as an interface to VBA (Excel application) from where it will called. This is what is my need and should tell me how to proceed i haven't this kinda of thing till now. I worked with dll's but not with C code. Previoulsy i created a dll using VB and used in VC++ and VB as well but never tried with C code. But now i need to do it with C code.

And also congrats for becoming top contributor.
Vulpes14y ago
Just to be clear are you saying that you want to reference an unmanaged C or C++ dll in a managed C++ application?

If so, are you compiling the C++/CLI application using mixed mode (/clr switch) or are you using the 'safe' or 'pure' modes?