Bot Framework Messages Controller without DI

MessagesController.cs

/// <summary>
/// POST: api/Messages
/// Receive a message from a user and reply to it
/// </summary>
public async Task<HttpResponseMessage> Post([FromBody]Activity activity)
  {
    if (activity.Type == ActivityTypes.Message)
    {
      await Conversation.SendAsync(activity, () => new Dialogs.RootDialog());
    }