title: System.Array. does not contain a definition for "ToList"
body: <p>I'm getting the above error on the ToList() line of the code below</p>
  
  <pre><code>if (emailReplyTo != null)
  {
    System.Collections.Generic.List&lt;String&gt; replyto
      = emailReplyTo
      // Strip uneccessary spaces
      .Replace(", ", ",")
      .Split(',')
      .ToList();
  
    request.WithReplyToAddresses(emailReplyTo);
  }
  </code></pre>
  
  <p>I have included <code>using System.Collections;</code> at the top of my file.
  The target framework is 3.5, so why is this causing an error?</p>