recog.cs

 private void StartRecordingAndRecognizing()
        {
            if(isNotContinious)
            {
                _timer = NSTimer.CreateRepeatingScheduledTimer(5, delegate
                {
                    DidFinishTalk();
                });
            }
            

            _recognitionTask?.Cancel();
            _recognitionTask = null;

            var audioSession = AVAudioSession.SharedInstance();
            NSError nsError;
            nsError = audioSession.SetCategory(AVAudioSessionCategory.Record);
            audioSession.SetMode(AVAudioSession.ModeMeasurement, out nsError);
            nsError = audioSession.SetActive(true, AVAudioSessionSetActiveOptions.NotifyOthersOnDeactivation);

            _recognitionRequest = new SFSpeechAudioBufferRecognitionRequest();

            var inputNode = _audioEngine.InputNode;
            if (inputNode == null)
            {
                throw new Exception();
            }

            var recordingFormat = inputNode.GetBusOutputFormat(0);
            inputNode.InstallTapOnBus(0, 1024, recordingFormat, (buffer, when) =>
            {
                _recognitionRequest?.Append(buffer);
            });

            _audioEngine.Prepare();
            _audioEngine.StartAndReturnError(out nsError);

            _recognitionTask = _speechRecognizer.GetRecognitionTask(_recognitionRequest, (result, error) =>
            {
                var isFinal = false;
                if (result != null)
                {
                    _recognizedString = result.BestTranscription.FormattedString;
                    MessagingCenter.Send<ISpeechToText, string>(this, "STT", _recognizedString);
                    Console.WriteLine("result");
                    if(isNotContinious)
                    {
                        _timer.Invalidate();
                        _timer = null;
                        _timer = NSTimer.CreateRepeatingScheduledTimer(3, delegate
                        {
                            DidFinishTalk();
                        });
                    }
                    
                }
                if (error != null || isFinal)
                {
                    MessagingCenter.Send<ISpeechToText>(this, "Final");
                    StopRecordingAndRecognition();
                }
            });

        }