How to resolve: error LNK2001: unresolved external symbol "public: static void *

[mlong30]

Hi All,

I'm trying to create a C++ DLL using the WinInet API, but for some odd reason, I get no errors during compiling but get external link errors regarding variables within my class. Any idea how I can resolve this? Visual Studio 2015.

----------------------------------------header test.h -------------------------------------------
// #include "stdafx.h"
using namespace std;
// #include
#include
#include
#include
#include
#include
#include
//#include
#pragma comment(lib, "wininet.lib")
#pragma comment(lib, "user32.lib")
#define FTP_FUNCTIONS_BUFFER_SIZE MAX_PATH+8

namespace Win32_FTP
{
class FTP_Win32_ClientV1
{
private:

    public:
                    static LPCWSTR sFileSearch;
                    static char \* sIpAddress;
                    static  LPCWSTR sUsername;
                    static LPCWSTR sPassword;
                    static string sRemoteDir;
                    static string sLocalDir;
                    static string sFilename;
                    static DWORD dwError;
                    static HINTERNET hFTPConnect;
                    static HINTERNET hFind;
                    static HINTERNET hConnect;

                    static HANDLE hFile;
                    static WIN32\_FIND\_DATA   FindFileData;
                    static string strTemp;


            static  \_\_declspec(dllexport) void Test1();
            static  \_\_declspec(dllexport) void FtpCloseConnection();

    };

}

----------------------------------------source test.cpp -------------------------------------------

//using namespace std;
#include
#include "test.h"
// using namespace std;

namespace Win32_FTP
{

    void FTP\_Win32\_Client::Test1()
    {
            cout << "This is a test from Cplus to Csharp DLL";
    }


    void FTP\_Win32\_Client::FtpCloseConnection()
    {

            InternetCloseHandle(FTP\_Win32\_Client::hFind);
            InternetCloseHandle(FTP\_Win32\_Client::hFTPConnect);
            InternetCloseHandle(FTP\_Win32\_Client::hConnect);
    }

}

***************************LINK ERRORS ************************
Test.obj : error LNK2001: unresolved external symbol "public: static void * Win32_FTP::FTP_Win32_Client::hFTPConnect" (?hFTPConnect@FTP_Win32_Client@Win32_F

[Victor Nijegorodov]

Have a look at [Linking errors while linking a dll in c++](https://social.msdn.microsoft.com/Forums/en-US/f3b696ec-2a9f-4c9f-a50c-92395008c3bf/linking-errors-while-linking-a-dll-in-c?forum=Vsexpressvc) and many other discussions here: [Google](https://www.google.com/search?newwindow=1&ei=LidlXLKjJYXFwQKnsrOYAw&q=error+LNK2001%3A+unresolved+external+symbol+dll+class&oq=error+LNK2001%3A+unresolved+external+symbol+dll+class&gs\_l=psy-ab.3...1008.15703..16700...4.0..0.505.1494.10j3j5-1......0....1..gws-wiz.......0i71j35i39j0i20i263j0j0i22i30j0i22i10i30j33i160j33i21.oA1rbIz38WU)

[CPallini]

Class static variables, like Win32_FTP::FTP_Win32_Client::hFTPConnect must be also defined in one source file. That is you have to write

HINTERNET Win32_FTP::FTP_Win32_Client::hFTPConnect;

(and so on...) in your test.cpp source file. An altrernative, available only with C++ 17 compliant compilers is to declare such variables inline inside the header file (see, for instance INLINE VARIABLES[^]).

[Lost User]

Why are you creating a class and then making everything static?

[Davie21240]

Definitely remove the line: using namespace std; My advice: NEVER do that.