convert word files to plain text c#

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 Microsoft.Office.Interop.Word;

namespace ReadWordDocProject
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string testFile = @"C:\Users\<mycomputer>\Documents\TestItemHelpers\TestWordDoc.docx";

            Microsoft.Office.Interop.Word.Application application = new Microsoft.Office.Interop.Word.Application();
            Document document = application.Documents.Open(testFile);//path here

            int count = document.Words.Count;
            for (int i = 1; i <= count; i++)
            {
                string text = document.Words[i].Text;
                //Do output with text here
                richTextBox1.AppendText(text);
            }

            ((_Application)application).Quit(); //cast as _Application because there's ambiguity 
        }


    }
}