LNK2019 error when trying to test a dll - c++

Question

I work with an application that appears (just started a few weeks ago, so I am still learning the older apps) to be built in C and my company wants to use that program's ability to make a call to an outside DLL to extend some new functionality. To do this, I started working on my POC, which is the first two files below. The only specification we were given was that the dll has to export the following function:
extern int __stdcall TestMethod_LoadCustomer(const char * name, char * id);
I tried to implement that as follows:
TestDLL.h
#define TestDLL_API __declspec(dllexport)
namespace TestDLL
{
class TestDLL
{
public:
static TestDLL_API int TestMethod_LoadCustomer(const char* name, char* id);
};
}
TestDLL.cpp
// TestDLL.cpp : Defines the exported functions for the DLL application.
//
#include "stdafx.h"
#include "TestDLL.h"
#include <string.h>
extern "C" int __declspec(dllexport) __stdcall TestMethod_LoadCustomer(const char* name, char* id)
{
if (strlen(name) <= 8) {
strcpy(id, name); // name contains customer id
} else {
id[0] = 0; // Customer not found
}
return 0;
}
These two files compile fine. The problem comes in when I try to test this dll via a separate little console app shown here:
RunTEST.cpp
// RunTest.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
#include "TestDLL.h"
using namespace std;
int _tmain()
{
char* id= "";
TestDLL::TestDLL::TestMethod_LoadCustomer("77777", id);
cout << id;
cin >> id;
return 0;
}
All I am looking for is to be able to pass in a character string into the call TestMethod_LoadCustomer() and have it be added to the id field.
When I actually try to build this solution, I get the following error:
"error LNK2019: unresolved external symbol "public: static int __cdecl TestDLL::TestDLL::TestMethod_LoadCustomer(char const *, char *)" (?TestMethod_LoadCustomer#TestDLL#1#SAHPBDAD#Z) referenced in function _wmain"
I am assuming it has something to do with the way I am trying to reference it in my client app, but I am not sure. I have looked at other LNK2019 errors on StackOverflow, but none of those solutions seemed to work here, of I have incorrectly implemented them. Can any one assist in helping me get rid of this error message?

Answer 1

On the TestDLL.cpp file is missing two things:
1) The namespace TestDLL.
2) the TestDLL:: before the method name.
// TestDLL.cpp : Defines the exported functions for the DLL application.
//
#include "stdafx.h"
#include "TestDLL.h"
#include <string.h>
namespace TestDLL {
extern "C" int __declspec(dllexport) __stdcall TestDLL::TestMethod_LoadCustomer(const char* name, char* id)
{
if (strlen(name) <= 8) {
strcpy(id, name); // name contains customer id
} else {
id[0] = 0; // Customer not found
}
return 0;
}
}

Answer 2

While defining the function in TestDLL.cpp you didn't mention that the function is member of the class TestDLL.