Calling Excel/DLL/XLL functions from C#

Question

I have a particular function in an Excel addin(xll). The addin is proprietary and we do not have access to the source code. However we need to call some functions contained

Answer 1

You might like to try XLL Plus http://www.planatechsolutions.com/xllplus/default.htm. It's a bit pricey, but the XLL Wrapper Libraries feature is exactly what you are looking for:

"Sometimes it is useful to be able to call your Excel add-in functions from other environments, such as command-line programs or interactive applications, written in C++, Java, C# or Visual Basic. The Xll Wrapper toolkit contains tools, a runtime library, samples and documentation to help with the development of COM modules and .NET assemblies that wrap Excel XLL add-ins"

Answer 2

You should be able to use reflection to get access to your addin. try using The Reflector to see what's available.

Answer 3

You need to create a fake xlcall32.dll, put it in the same directory as your XLL (do not put excel's own xlcall32.dll in the PATH). Here is some code:

# include <windows.h>

typedef void* LPXLOPER;

extern "C" void __declspec(dllexport) XLCallVer ( ) {}

extern "C" int __declspec(dllexport) Excel4 (int xlfn, LPXLOPER operRes, int count,... ) { return 0; }

extern "C" int __declspec(dllexport) Excel4v(int xlfn, LPXLOPER operRes, int count, LPXLOPER far opers[]) {return 0;}

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Now suppose I have an XLL called xll-dll.xll with a function called (use "depends.exe" to find out the names of the exported functions) xlAdd that well adds two doubles: extern "C" __declspec(dllexport) XLOPER * __cdecl xlAdd(XLOPER* pA, XLOPER* pB);

The following code calls it:

---

# include <windows.h>
# include <iostream>

// your own header that defines XLOPERs
# include <parser/xll/xloper.hpp>

// pointer to function taking 2 XLOPERS
typedef XLOPER * (__cdecl *xl2args) (XLOPER* , XLOPER* ) ;

void test(){
/// get the XLL address
HINSTANCE h = LoadLibrary("xll-dll.xll");
if (h != NULL){
xl2args myfunc;
/// get my xll-dll.xll function address
myfunc = (xl2args) GetProcAddress(h, "xlAdd");
if (!myfunc) { // handle the error
FreeLibrary(h); }
else { /// build some XLOPERS, call the remote function
XLOPER a,b, *c;
a.xltype = 1; a.val.num = 1. ;
b.xltype = 1; b.val.num = 2. ;
c = (*myfunc)(&a,&b);
std::cout << " call of xll " << c->val.num << std::endl; }
FreeLibrary(h); }
}

int main()
{test();}

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My exe actually works (to my own surprise), and output 3 as expected. You must have some knowledge of what your XLL actually expects for parameters. If it allocates some memory, you must check if the #define xlbitDLLFree 0x4000 is set on your XLOPER c->type, and call back "xlAutoFree".

Answer 4

An Excell add-in DLL might be written in C#. If so, then you can probably bypass Excel altogether. Might need a wrapper though.

Answer 5

check whether assembly is available in program files where you install the plguin, reference that assembly directly to your c# project - check the object browser for your class, method or object