title: c++ singleton attempt: unresolved external symbol
body: <p>I am a c# developper trying to do c++ things and I cannot understand the issue here:</p>
  
  <pre><code>namespace myNamespace
  {
      class Application
      {
      private:
          Application(void);
          ~Application(void);
  
          // Not copyable
          Application(const Application&amp;);
          Application&amp; operator= (const Application&amp;);
  
          static Application _instance; 
  
          [...]
  
      public:
          static Application&amp; current(void);
      };
  }
  </code></pre>
  
  <p>(this is supposed to be a singleton...)</p>
  
  <p>and this causes the error:
  "<strong>error LNK2001: unresolved external symbol "private: static class myNamespace::Application myNamespace::Application::_instance" (?_instance@Application@myNamespace@@0V12@A)</strong>"</p>
  
  <p>Is it because I am using the class I am declaring in the class declaration?</p>
  
  <p>Thanks a lot!</p>