title: Visual C++ Express 2010 suddenly won't accept #includes
body: <p>I'm working with an API which has <code>#define</code>ed all their include files. I'm developing in Visual C++ 2010 Express, and it's been working fine up till now.</p>
  
  <p>I was adding a new cpp-file to the project, and accidentally added a "Windows Form" instead. VC warned me that my project was not using CLR at the moment, did I really want to? I clicked no, and added the file as intended. After that, however, my project no longer compiles. </p>
  
  <p>The code looks basically like this:</p>
  
  <p><strong>api_header.h</strong>:</p>
  
  <pre><code>#define DEFINED_HEADER_NAME "path/to/header/file.h"
  </code></pre>
  
  <p><strong>stdhpf.h</strong>:</p>
  
  <pre><code>#include DEFINED_HEADER_NAME
  </code></pre>
  
  <p>As I said, worked fine for a long time. Now I get this:</p>
  
  <blockquote>
    <p>error C2006: <code>'#include'</code> : expected a filename, found <code>'identifier'</code><br>
    fatal error C1083: Cannot open include file: <code>''</code>: No such file or directory</p>
  </blockquote>
  
  <p>What is causing this? I found some post that said it was because of having turned on precompiled headers, but I checked <code>Project properties &gt; Configuration properties &gt; C/C++ / Precompiled headers</code>, and it's off (I mention the setting path since I'm new to VS, there might be more than one way to do it...).</p>
  
  <p>Any ideas?</p>