Question

I have .lib file with its header (.h) file. This file have a few functions that need to be used in C# application.

After googling I found that I need to create a dynamic DLL from this static library and call this dynamic DLL from C# code using interop.

1. I have created a win32 project and selected type DLL.

2. Included header file and added .lib to additional dependencies.

   I am able to see the functions defined in the static library (when I press ctrl + space).

As a total newbie I do not know how I can export the function, which is, in .lib with following signature:

void testfun( char* inp_buff, unsigned short* inp_len, char* buffer_decomp,unsigned *output_len,unsigned short *errorCode)

I want same signature in my dynamic DLL with a different name.

What to write in header file and .cpp file?

Answer 1

If you can recompile your lib, just add __declspec(dllexport) to the signatures of all of the functions you want to be exported.

void __declspec(dllexport) testfun( char* inp_buff, unsigned short* inp_len, char* buffer_decomp,unsigned *output_len,unsigned short *errorCode)

If you can’t do that, then you can export them by writing a .def file instead. Using def files you can even change the name of a function as it is exported.
http://msdn.microsoft.com/en-us/library/28d6s79h.aspx

—- contents of mylib.def —-

LIBRARY

EXPORTS
   testfun
   newname=testfun2

Then when you link the dll, include mylib.def

link /dll /machine:x86 /def:mylib.def  mylib.lib

Edit2:

note that pinvoke assumes that the functions you import will have _stdcall calling convention unless you say otherwise. So you might need to do this as well, in your C# code.

[DllImport("mylib.dll", CallingConvention=CallingConvention.Cdecl)]

Or, you could change your C++ code to be __stdcall

void __declspec(dllexport) __stdcall testfun( char* inp_buff, ...