how to store using input with System.Speech ??

Question

HI ive got the following questio, i'm trying to program an simple calculator based on SpeechRecognizion . I can let is speak but how can i store the user input in a variable ?

 

here is my code so far

 

using System;
using System.IO;
using System.Speech.Recognition;
using System.Speech.Synthesis;

namespace calculator
{
    class Program
    {
        public static SpeechSynthesizer S = new SpeechSynthesizer();
        public static SpeechRecognitionEngine rec = new SpeechRecognitionEngine();

        static void Main(string[] args)
        {
            S.SelectVoiceByHints(VoiceGender.Neutral);
            S.Speak("What calculation should i do for you");

            var calculationslist = new Choices();
            calculationslist.Add(File.ReadAllLines(@"C:\Program Files\DK's Soft\JARVIS system Commands\calculation commands\calculationcommands.txt"));

            var gr = new Grammar(new GrammarBuilder(calculationslist));

            try
            {
                rec.RequestRecognizerUpdate();
                rec.LoadGrammar(gr);
                rec.SetInputToDefaultAudioDevice();
                rec.RecognizeAsync(RecognizeMode.Multiple);

                var userinput = ???

            }
            catch (Exception)
            {
                return;
            }
        }

    }
}