auth.cs

private void AskForSpeechPermission()
        {
            SFSpeechRecognizer.RequestAuthorization((SFSpeechRecognizerAuthorizationStatus status) =>
            {
                switch (status)
                {
                    case SFSpeechRecognizerAuthorizationStatus.Authorized:
                        MessagingCenter.Send<ISpeechToText>(this, "Authorized");
                        break;
                    case SFSpeechRecognizerAuthorizationStatus.Denied:
                        throw new Exception("Audio permission denied");

                    case SFSpeechRecognizerAuthorizationStatus.NotDetermined:
                        throw new Exception("Audio permission not available");
                    case SFSpeechRecognizerAuthorizationStatus.Restricted:
                        throw new Exception("Audio permission denied");
                }
            });
        }