title: How to render optional text in string interpolation
body: <p>I have this which works fine:</p>
  <pre><code>var firstName = &quot;Greg&quot;;
  var ipAddress = &quot;0.0.0.0&quot;;
  
  var sql = @$&quot;sp_create_enrollment @first_name = '{firstName}',
          @ip_address = '{ipAddress}'&quot;;
  
  Console.WriteLine(sql);
  </code></pre>
  <p>This produces:</p>
  <p><code>sp_create_enrollment @first_name = 'Greg', @ip_address = '0.0.0.0'</code></p>
  <p>However, if ip_address is null, I need it to produce this:</p>
  <p><code>sp_create_enrollment @first_name = 'Greg', @ip_address = null</code></p>
  <p>Note that there are no quotes around the null, otherwise it gets passed as a string.</p>
  <p>How do I achieve that?</p>