title: Visual Studio compile and run even with #include error
body: <p>I am testing a software library (OpenCV 2.4.9) in Visual Studio 2012 Pro. Using a sample code, I wanted to test if the installation and library linking was correctly done in VS.</p>
  
  <p>I've got an #include error. I only include the following, no direct call elsewhere:</p>
  
  <pre><code>#include "stdfax.h"
  #include "opencv2\highgui\highgui.hpp"
  </code></pre>
  
  <p>So the error is: Cannot open source file "opencv2\highgui\highgui.hpp"<br>
  and all function names in my code are underlined too (which is normal).</p>
  
  <p>Normally, it would be a linker error and trying to build the program wouldn't work. But, to my surprise, the program builds without error and, more intriguingly, most of the program works correctly, including functions that are included in the "highgui.hpp" library that was not found. The file exists, btw.</p>
  
  <p>I have posted the question to OpenCV Forum but it could simply be a Visual Studio problem, so here I am guys!</p>
  
  <p><strong>Edit</strong><br>
  While I get no compiler error during building, I've got a lot of<br>
  'Loaded 'C:\Windows\System32\VARIOUS_NAMES.dll'. Cannot find or open the PDB file.  </p>
  
  <p><strong>Edit 2</strong><br>
  I commented the<br>
      <code>#include "opencv2\highgui\highgui.hpp"</code><br>
  statement and the code won't compile (since it doesn't recognize any of the function in the code). Makes me wonder if the problem isn't with Intellisense...</p>
  
  <p><strong>Edit 3</strong>  </p>
  
  <p>This was not Intellisense. Found the answer (below) and it works.</p>