Botframework v4: не удается отобразить карты

Это образец документации Botframework v4. Но это не работает. В эмуляторе бота Microsoft написано «Can't Render Card». Я пытаюсь сделать carouselCard, но эта простая карта из образца Microsoft уже не работает.

    {
  "type": "message",
  "text": "Plain text is ok, but sometimes I long for more...",
  "attachments": [
    {
      "contentType": "application/vnd.microsoft.card.adaptive",
      "content": {
        "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
        "type": "AdaptiveCard",
        "version": "1.0",
        "body": [
          {
            "type": "TextBlock",
            "text": "Hello World!",
            "size": "large"
          },
          {
            "type": "TextBlock",
            "text": "*Sincerely yours,*"
          },
          {
            "type": "TextBlock",
            "text": "Adaptive Cards",
            "separation": "none"
          }
        ],
        "actions": [
          {
            "type": "Action.OpenUrl",
            "url": "http://adaptivecards.io",
            "title": "Learn More"
          }
        ]
      }
    }
  ]
}

Однако, если я удалю верхнюю часть кода, этот код будет работать:

  {
  "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
  "type": "AdaptiveCard",
  "version": "1.0",
  "body": [
    {
      "type": "TextBlock",
      "text": "Hello World!",
      "size": "large"
    },
    {
      "type": "TextBlock",
      "text": "*Sincerely yours,*"
    },
    {
      "type": "TextBlock",
      "text": "Adaptive Cards",
      "separation": "none"
    }
  ],
  "actions": [
    {
      "type": "Action.OpenUrl",
      "url": "http://adaptivecards.io",
      "title": "Learn More"
    }
  ]
}

Так я называю карту. Есть лучший способ сделать это?

 public class GetNameAndAgeDialog : WaterfallDialog
    {

        private readonly string _cards = @".\Resources\TryCarouselCard.json";

        private static Attachment CreateAdaptiveCardAttachment(string filePath)
        {
            var adaptiveCardJson = File.ReadAllText(filePath);
            var adaptiveCardAttachment = new Attachment()
            {
                ContentType = "application/vnd.microsoft.card.adaptive",
                Content = JsonConvert.DeserializeObject(adaptiveCardJson),
            };
            return adaptiveCardAttachment;
        }

        public GetNameAndAgeDialog(string dialogId, IEnumerable<WaterfallStep> steps = null) : base(dialogId, steps)
        {

            AddStep(async (stepContext, cancellationToken) =>
            {
                var cardAttachment = CreateAdaptiveCardAttachment(_cards);
                var reply = stepContext.Context.Activity.CreateReply();
                reply.Attachments = new List<Attachment>() { cardAttachment };
                await stepContext.Context.SendActivityAsync(reply, cancellationToken);
                return await stepContext.ContinueDialogAsync();
            });
         }
      }