title: Preprocessor Directives in .Net Core for multiple frameworks
body: <p>I am trying to port several libraries from .NET Framework 4.0 to .NET Core, and saw that one of the useful things you can do is add things like the following that will conditionally compile portions of your code:</p>
  
  <pre><code>#if NETCOREAPP1_0
      do something
  #elif NET40
      do something else
  #endif
  </code></pre>
  
  <p>My question is what to put in place of the <code>NET40</code> in the code above. I have only been able to get <code>NETCOREAPP1_0</code> and <code>NETSTANDARD1_6</code> to be recognized. Every other thing I've put in for the <code>NET40</code> hasn't worked, including <code>net40</code>, <code>NET40</code>, <code>NET4_0</code>, and a few others. Is there a list somewhere that would give guidance on how to reference it? Or is there additional steps I need to take in another portion of the project to get it to recognize <code>net40</code>?</p>