title: What is .NET Portable Subset (Legacy)?
body: <p>Object browser in Visual Studio 2012 offers two different component sets for Portable class libraries:</p>
  
  <ul>
  <li>.NET Portable Subset</li>
  <li>.NET Portable Subset (Legacy)</li>
  </ul>
  
  <p>When I create Portable Class Library it uses .NET Portable Subset. What is the second set and how can I use it? It contains MEF which <a href="https://stackoverflow.com/questions/12483686/how-to-use-mef-in-portable-class-library">is not available in .NET Portable Subset</a>.</p>