title: String interpolation doesn't work with .NET Framework 4.6
body: <p>I just installed the .NET Framework 4.6 on my machine and then created a ConsoleApplication targeting .NET Framework 4.6 with Visual Studio 2013.</p>
  
  <p>I wrote the following in the <code>Main</code> method:</p>
  
  <pre><code>  string test = "Hello";
    string format = $"{test} world!";
  </code></pre>
  
  <p>But this does not compile. Doing the same in Visual Studio 2015 works.<br>
  Why?</p>