c# - Unable to start recognition: At least one grammar must be loaded before doing a recognition

Question

I was trying to make a basic voice recognition application but I'm stuck with an error. When I click the Enable button I get the following error: At least one grammar must be loaded before doing a recognition

even though I set up and loaded one. Anybody can help me out?

This is my code:

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.Recognition;

namespace Voice_Recognition
{
    public partial class Form1 : Form
    {
        SpeechRecognitionEngine recEngine = new SpeechRecognitionEngine();
        public Form1()
        {
            InitializeComponent();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            recEngine.RecognizeAsyncStop();
            btnDisable.Enabled = false;
        }

        private void richTextBox1_TextChanged(object sender, EventArgs e)
        {
            Choices commands = new Choices();
            commands.Add(new String[] { "Say Hello", "Print my name" });
            GrammarBuilder gBuilder = new GrammarBuilder();
            gBuilder.Append(commands);
            Grammar grammar = new Grammar(gBuilder);

            recEngine.LoadGrammar(grammar);
            recEngine.SetInputToDefaultAudioDevice();
            recEngine.SpeechRecognized +=new EventHandler<SpeechRecognizedEventArgs>(recEngine_SpeechRecognized);

        }

        private void button1_Click(object sender, EventArgs e)
        {
            recEngine.RecognizeAsync(RecognizeMode.Multiple);
            btnDisable.Enabled = true;
        }
        void recEngine_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
        {
            switch (e.Result.Text)
            {
                case "Say Hello":
                    MessageBox.Show("Hello Andrea");
                    break;
                case "Print my name":
                    richTextBox1.Text += "
Andrea";
                    break;
            }
        }
    }
}

Answer 1

Place the code from the richTextBox1_TextChanged method in the Form1 constructor instead. As it stands, the grammar is being reloaded every time the text is changed but it isn't being loaded when the program starts (and the method hookup code will be called multiple times for no reason). So if you were to click the button before typing anything into the box, there would be no grammar instantiated yet.