Is it possible to use DllImport to access namespaces?

Question

I just created an unmanaged C++ DLL and am trying to use DllImport in my C# app to access the function calls. However, each function belongs to its own namespace (there are multiple header files, multiple namespaces, multiple class files). When I try calling the function DllImport it says the entry point can't be found, and I can't help but feel it has to do with namespaces. How do I call my functions using their unique namespaces? Thanks.

Can you provide some code please? – Odys Jun 13 '13 at 22:44 — Odys, Jun 13 '13 at 22:44
I assume you're exporting your functions correctly? – Simon Whitehead Jun 13 '13 at 22:45 — Simon Whitehead, Jun 13 '13 at 22:45

score 3 · Answer 1 · answered Jun 13 '13 at 22:51

3

If you want to check the exported names of your functions you can use:

dumpbin /exports my_native_lib.dll

If it does not display any exports, there is something wrong with the way the functions are exported and we'll need more code.

answered Jun 13 '13 at 22:51

Pragmateek

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score 2 · Answer 2 · edited May 23 '17 at 12:13

2

DllImport will work for 'global' C functions, not C++ classes - for C++ classes you'll have to create C wrappers for the functions you need. See: using a class defined in a c++ dll in c# code

edited May 23 '17 at 12:13

Community

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answered Jun 13 '13 at 22:57

Dave Doknjas

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score 1 · Answer 3 · answered Jun 18 '13 at 08:51

1

you can use dependency walker to see the exported functions names of any dll. this way you could call on mangled function names.

answered Jun 18 '13 at 08:51

geva30

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score 0 · Answer 4 · answered Nov 14 '22 at 07:23

The answer is yes in VS 2022, I did not check earlier version. Sorry if this is late.

I used this construct for C# to access a public static method of a class within a namespace.

namespace LifetimeCallsCs {
internal sealed class NativeSimple {
    private NativeSimple() { }
    [DllImport("CppTransforms.dll", EntryPoint = "?LifetimeTransformCreate@LifetimeTransform@SimpleNS@@SAXPEAPEAX@Z", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true, SetLastError = false)]
    public static unsafe extern void* LifetimeTransformCreate(void** handle);
    [DllImport("CppTransforms.dll", EntryPoint = "?LifetimeTransformDelete@LifetimeTransform@SimpleNS@@SAXPEAX@Z", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true, SetLastError = false)]
    public static unsafe extern void LifetimeTransformDelete([In] IntPtr handle);
}

}

The argument EntryPoint = "...." specified the mangled method call.

the include file for c++ is:

namespace SimpleNS {

class LifetimeTransform
{
public:
    static void __declspec(dllexport) _cdecl LifetimeTransformCreate(void** handle);
    static void __declspec(dllexport) _cdecl LifetimeTransformDelete(void* handle);
};

}

The C++ code is:

namespace SimpleNS {
void LifetimeTransform::LifetimeTransformCreate(void** handle) {
    *handle = new SimpleNS::LifetimeTransformImp();
}
void LifetimeTransform::LifetimeTransformDelete(void* handle) {
    if (handle != nullptr)
        delete (SimpleNS::LifetimeTransformImp*)handle;
}

}

you can use dependency walker to see the exported functions names of any dll. this way you could call on mangled function names.

Is it possible to use DllImport to access namespaces?

4 Answers4

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