Required files to compile in a C++ project:

crsysapi.hpp
diCryptoSys.h
crsysapi.cpp
  #include "diCryptoSys.h"
  #include "crsysapi.hpp"
{main}.cpp
  #include "crsysapi.hpp"
  int main() { ... }

You must link to diCryptoSys.lib. In MSVC++ IDE, use Project > Properties > Linker > Input > Additional Dependencies and add the full path to diCryptoSys.lib. E.g.

Additional Dependencies = $(OutDir)diCryptoSys.lib;%(AdditionalDependencies)

Using the command-line with MSVC:

CL test.cpp crsysapi.cpp /link ..\Debug\diCryptoSys.lib

Using GCC (make sure the DLL has been compiled for target X64):

g++ -std=c++11 test.cpp crsysapi.cpp "C:\fullpath\to\x64\Debug\diCryptoSys.lib"

Here is a simple C++ (STL) program for testing.

#include <iostream>
#include "crsysapi.hpp"
int main()
{
    std::cout << "Gen::Version=" << crsysapi::Gen::Version() << std::endl;
}