Закрытие WORD приложения - C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;
using Microsoft.Office.Interop.Word;
 
namespace kolontitul
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            
            textBox1.Text = folderBrowserDialog1.SelectedPath;
            string selc_path;
            selc_path = folderBrowserDialog1.SelectedPath;
            string[] pathes = Name_Path_file(selc_path);
            ParallelOptions ns = new ParallelOptions();
            ns.MaxDegreeOfParallelism = 5;
            Parallel.For(0, pathes.Length, ns,i =>
            {
                colontit(pathes[i]);
 
            });
        }
       
        public string[] Name_Path_file(string path)
        {
 
           string [] file_name = System.IO.Directory.GetFiles(path, "*.doc", SearchOption.AllDirectories);
            return file_name;
        }

        public void colontit(string path) 
        {
            object file = @path;
            object nullobj = System.Reflection.Missing.Value;
            object missing = System.Reflection.Missing.Value;
            object format = Microsoft.Office.Interop.Word.WdSaveFormat.wdFormatDocument;

            ApplicationClass wordApp = new ApplicationClass();
            Document doc = wordApp.Documents.Open(
                ref file, ref nullobj, ref nullobj,
                ref nullobj, ref nullobj, ref nullobj,
                ref nullobj, ref nullobj, ref nullobj,
                ref nullobj, ref nullobj, ref nullobj,
                ref nullobj);
 
            wordApp.ActiveDocument.Sections[1].Footers[Microsoft.Office.Interop.Word.WdHeaderFooterIndex.wdHeaderFooterPrimary].
Range.Text = "cyberforum - место, где Вам всегда помогут.";
            wordApp.Visible = false;

            object save = Microsoft.Office.Interop.Word.WdSaveOptions.wdSaveChanges;
            object orform = Microsoft.Office.Interop.Word.WdSaveFormat.wdFormatDocument;
            doc.Close(ref save,ref orform, nullobj);
            
            wordApp.Quit(save, orform, nullobj);
        
        }

    }
}