title: Twilio Twiml(response) gives xml exception
body: <p>After updating my Twilio nuget package to 5.8.0, I'm getting an error when trying to return TwiML. </p>
  
  <pre><code>        var response = new MessagingResponse();
          response.Message("Hello world");
          return TwiML(response);
  </code></pre>
  
  <p>This code breaks in Visual Studio and throws an XML exception at line 1 position 1. The code before the update:</p>
  
  <pre><code>        var response = new VoiceResponse();
          response.Sms("Hello world");
          return TwiML(response);
  </code></pre>
  
  <p>Worked exactly as expected, but now throws the same error. What am I missing here?</p>
  
  <p>EDIT</p>
  
  <p>So I created a whole new MVC project that uses Twilio v5.8.0. This is the all that I added:</p>
  
  <pre><code>public class HomeController : TwilioController
  {
      // GET: Home
      public ActionResult Index()
      {
          return View();
      }
  
      [HttpPost]
      public ActionResult Text()
      {
          var response = new VoiceResponse();
          response.Sms("Hello world");
          return TwiML(response);
      }
  }
  </code></pre>
  
  <p>This gives me the same error as before. </p>
  
  <p>When I switched back to v5.7.2 it works fine.</p>