title: Visual Studio "Organize Usings | Remove and Sort" falsely reports error
body: <p>In various code files of various projects, Visual Studio sometimes gives an error message when I tell it to remove and sort the usings of the code file. The message:</p>
  
  <blockquote>
    <p>"Your project or one of its references does not currently build. If you
    continue with this operation, required usings may be removed."</p>
  </blockquote>
  
  <p>However, this is not true. Required usings are not removed when telling VS to continue, and the project <em>does</em> build.</p>
  
  <p>I have Googled this issue, looked in MSDN, and tried to figure out why I get this on certain code files but not others, but no no avail.</p>
  
  <p>Has anyone else encountered this, and if so, any ideas what this is about?</p>
  
  <p>Ps. I am running VS 2012 Ultimate, but I saw this from at least 2005.</p>