title: Cannot open source file; C++; Visual Studio
body: <p>I'm learning about dll files and trying to create one. 
  My problem is that when i try to build my solution in visual studio, i'm getting errors saying e.g. "cannot open source file string.h".</p>
  
  <p>This happens for multiple header files.  The error is produced by a file other than mine, which includes string.h</p>
  
  <p><a href="https://i.stack.imgur.com/sj8o4.png" rel="nofollow noreferrer">error list from VS</a></p>
  
  <p>I can't figure out how to fix this error, and any help will be greatly appreciated! </p>