title: How can I fix "System does not contain a definition for 'Text" error
body: <p>Revisiting some code that I haven't touched in a few weeks and now when I go to build it I get a few errors, one of them being:
   Code CS0117 'myNamespace.System' does not contain a definition for 'Text'
  when trying the line:</p>
  
  <pre><code>string aFieldTitle = System.Text.RegularExpressions.Regex.Replace((string)af.title, "[^A-Za-z0-9_]", "").ToUpper();
  </code></pre>
  
  <p>I've already searched for reference(s) to add, but I don't see one for System.Text in the Reference Manager.</p>