Convert Speech To Text using c#

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C#

I have written the following code to perform speech recognition using the Speech API built into .NET, but it's not recognising speech. Could you please help?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Speech;
using System.Speech.Synthesis;
using System.Speech.Recognition;
using System.Speech.Recognition.SrgsGrammar;
using System.Threading;


namespace SpeechToText
{
    public partial class Form1 : Form
    {
        SpeechSynthesizer sSynth = new SpeechSynthesizer();
        PromptBuilder pBuilder = new PromptBuilder();
        SpeechRecognitionEngine sRecognize = new SpeechRecognitionEngine();
       
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
          pBuilder.ClearContent();
            pBuilder.AppendText(textBox1.Text);
            sSynth.Speak(pBuilder);
        }

        private void button2_Click(object sender, EventArgs e)
        {
           button2.Enabled = false;
            button3.Enabled= true;
            Choices sList = new Choices();
            sList.Add(new string[] { "hello","hi","how","are","you","srinivas","test","i"});
            Grammar gr = new Grammar(new GrammarBuilder(sList));
            try
            {
                sRecognize.RequestRecognizerUpdate();
                sRecognize.LoadGrammar(gr);
                sRecognize.SpeechRecognized += sRecognize_SpeechRecognized;

                sRecognize.SetInputToDefaultAudioDevice();
                sRecognize.RecognizeAsync(RecognizeMode.Multiple);

            }
            catch
            {
                return;
            }
          /*  sRecognize.SetInputToDefaultAudioDevice();
            sRecognize.LoadGrammar(new DictationGrammar());
            sRecognize.SpeechRecognized += new EventHandler(sRecognize_SpeechRecognized);
            sRecognize.RecognizeAsync(RecognizeMode.Multiple);*/

        }

        void sRecognize_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
        {
           /* foreach (RecognizedWordUnit word in e.Result.Words)
            {
                listBox1.Items.Add(word.Text);
            }*/
            if (e.Result.Text == "exit")
            {
                Application.Exit();
            }
            else
            {
                textBox1.Text = textBox1.Text + " " + e.Result.ToString();
            }
        }

       

        private void Form1_Load(object sender, EventArgs e)
        {
          // sRecognize.SpeechRecognized += new EventHandler(sRecognize_SpeechRecognized);

        }

       
       
    }
}