title: Visual C++ - one or more multiply defined symbols found
body: <p>Whenever I start to build my dll I get this error:
  fatal error LNK1169: one or more multiply defined symbols found</p>
  
  <p>I think there's nothing wrong with the code because I copied it from a source:</p>
  
  <p>ExoDll1.cpp</p>
  
  <pre><code>#include "stdafx.h"
  
  double BoxArea(double L, double H, double W);
  double BoxVolume(double L, double H, double W);
  extern "C" __declspec(dllexport)void BoxProperties(double Length, double Height,
                                  double Width, double&amp; Area, double&amp; Volume);
  
  BOOL APIENTRY DllMain( HANDLE hModule, 
                     DWORD  ul_reason_for_call, 
                     LPVOID lpReserved
                   )
  {
      return TRUE;
  }
  
  double BoxArea(double L, double H, double W)
  {
      return 2 * ((L*H) + (L*W) + (H*W));
  }
  
  double BoxVolume(double L, double H, double W)
  {
      return L * H * W;
  }
  
  void BoxProperties(double L, double H, double W, double&amp; A, double&amp; V)
  {
  A = BoxArea(L, H, W);
  V = BoxVolume(L, H, W);
  }
  </code></pre>
  
  <p>I tried to create a new project and delete the old ones but same problem still exists.. What seems to be the problem?</p>