title: Add existing project to solution "read only" in Visual Studio
body: <p>Is it possible to add an existing project to a solution in "read-only" mode?</p>
  
  <p>I got access to a big bunch of internal projects, from which I just need some functions for another solution. Since I'm new to the original solution I'd like to make sure I don't accidentally change any of the existing files and check them into the TFS. </p>
  
  <p>The easiest way to do so, would be some sort of "Add existing project (read only)"-Function.
  Is there any way to do so? Or are there any other ways to ensure I'm not accidentally changing any of the existing files?</p>
  
  <p>I'm using MS Visual Studio 2013 Professional. </p>