Question

I get these three errors and they seem to make little sense to me. If i comment the UserInstruction1(P1, P2, P3); in the console app the errors go away. Both projects are /CLR projects.

error LNK2028: unresolved token (0A000930) "void __cdecl UserInstruction1(double *,wchar_t *,wchar_t *)" (?UserInstruction1@@$$FYAXPANPA_W1@Z) referenced in function "int __cdecl wmain(int,wchar_t * * const)" (?wmain@@$$HYAHHQAPA_W@Z)  

error LNK2019: unresolved external symbol "void __cdecl UserInstruction1(double *,wchar_t *,wchar_t *)" (?UserInstruction1@@$$FYAXPANPA_W1@Z) referenced in function "int __cdecl wmain(int,wchar_t * * const)" (?wmain@@$$HYAHHQAPA_W@Z)

error LNK1120: 2 unresolved externals   C:\Workspace\Company.Pins\Bank\Source\Debug\Company.Pins.Bank.Win32Console.exe

//Console App.
#include "stdafx.h"
#include "UInstruction.h"



int _tmain(int argc, _TCHAR* argv[])
{
    auto P2 = (TCHAR *)"3 Barrowstead";
    TCHAR* P3;
    double* P1;
    P1[0] = 13;

    UserInstruction1(P1, P2, P3);
    return 0;
}

—

//UInstruction.h
#ifndef __UINSTRUCTION_H__
#include "stdafx.h"
#include "UInstruction.h"
#include "common.h"

#include <iostream>
#include <stdio.h>
#define PRES_NOCOMMAND_FOUND 2000


#define DllExport  __declspec(dllexport)

void ReconcileUHParameter(const double* lpNumeric, TCHAR* lpAlpha1, TCHAR* lpAlpha2);
extern void UserInstruction1(double* lpNumeric,     TCHAR* lpAlpha1, TCHAR* lpAlpha2);

#endif

—

//UInstruction.cpp
#include "stdafx.h"
#include "UInstruction.h"
#include "common.h"
#using "Company.Pins.Bank.Decryption.dll"
#include <iostream>
#include <stdio.h>
using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;


CPReSInterfaceApp theApp;
extern void UserInstruction1(
                    double* lpNumeric, 
                    TCHAR* lpAlpha1, TCHAR* lpAlpha2)
{
//logic goes here       
}

Answer 1

I assume here that all code resides in a single project (Company.Pins.Bank.Win32Console). If so you should move the <\iostream> and <\stdio.h> includes (and any other includes of headers that never/seldom change to stdafx.h:

//stdafx.h

#include <iostream>
#include <stdio.h>


//other headers that are widely used but never/seldom change...

#define DllExport  __declspec(dllexport)
#define DllImport  __declspec(dllimport)

and

//UInstruction.h

#pragma once //you are in VS 2010...

#include "common.h"

//ommited code for brevity...
void UserInstruction1(double* lpNumeric,     TCHAR* lpAlpha1, TCHAR* lpAlpha2);

and

//UInstruction.cpp
#include "stdafx.h"
#include "UInstruction.h"

//ommitted code for brevity...

void UserInstruction1( double* lpNumeric, 
                       TCHAR* lpAlpha1, TCHAR* lpAlpha2 )
{
   //logic goes here
}

If UserInstruction1 resides in a Dll that is used by the Company.Pins.Bank.Win32Console project:

Make sure you define in stdafx.h for the dll and console projects:

#define DllExport  __declspec(dllexport)
#define DllImport  __declspec(dllimport)

Open the properties for the DLL project, go to “Configuration Properties” -> “C/C++” -> “Preprocessor” and add to “Preprocessor Definitions” a preprocessor symbol (if you don’t have one). I.e. I’ll call it MY_DLL. Don’t forget to define it in all configurations…

Make sure you export the functions from the Dll

//UInstruction.h

#pragma once //you are in VS 2010...

#ifdef MY_DLL
    #define MY_DLL_EXPORTS  DllExport
#else
    #define MY_DLL_EXPORTS  DllImport
#endif //MY_DLL

#include "common.h"

#define PRES_NOCOMMAND_FOUND 2000

//ommited code for brevity...

void MY_DLL_EXPORTS UserInstruction1(double* lpNumeric,     TCHAR* lpAlpha1, TCHAR* lpAlpha2);

The cpp file for UInstruction remains the same as above…

EDIT: For completness…

//UInstruction.cpp
#include "stdafx.h"
#include "UInstruction.h"

//ommitted code for brevity...

//no extern needed...
void UserInstruction1( double* lpNumeric, 
                       TCHAR* lpAlpha1, TCHAR* lpAlpha2 )
{
   //logic goes here
}

Do not forget to add a reference to the Dll project to the Company.Pins.Bank.Win32Console project from the properties of the Company.Pins.Bank.Win32Console “Common Properties” -> “Framework and References”