title: `Add-Type` C# 6+ features throwing errors
body: <p>I am trying to compile <a href="/questions/tagged/c%23" class="post-tag" title="show questions tagged &#39;c#&#39;" rel="tag">c#</a> source code in <a href="/questions/tagged/powershell" class="post-tag" title="show questions tagged &#39;powershell&#39;" rel="tag">powershell</a> by using this command:</p>
  
  <pre><code>Add-Type -ReferencedAssemblies $assemblies -TypeDefinition $source
  </code></pre>
  
  <p>But <a href="/questions/tagged/c%23-6.0" class="post-tag" title="show questions tagged &#39;c#-6.0&#39;" rel="tag">c#-6.0</a> features are not working, for example:</p>
  
  <blockquote>
    <p><code>Add-Type : c:\Users\...\AppData\Local\Temp\2\d2q5hn5b.0.cs(101) : Unexpected character '$'</code></p>
  </blockquote>
  
  <p>For code:</p>
  
  <pre><code>new Problem($"... ({identifier})", node)
  </code></pre>
  
  <p>I am using <a href="/questions/tagged/powershell-v5.1" class="post-tag" title="show questions tagged &#39;powershell-v5.1&#39;" rel="tag">powershell-v5.1</a></p>
  
  <p>Is there a way to fix this?</p>