C#读取Word并在指定位置插入文本

using System;
using System.IO;
using System.Reflection;
using MWord = Microsoft.Office.Interop.Word;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            MWord.Application app = new Microsoft.Office.Interop.Word.Application();
            MWord.Document doc = null;
            object unknow = Type.Missing;
            app.Visible = true;
            string str = @"F:2.doc";
            object file = str;
            doc = app.Documents.Open(ref file,
                ref unknow, ref unknow, ref unknow, ref unknow,
                ref unknow, ref unknow, ref unknow, ref unknow,
                ref unknow, ref unknow, ref unknow, ref unknow,
                ref unknow, ref unknow, ref unknow);

            


            object bk = "电话";       //word书签
            if (doc.Bookmarks.Exists("电话"))
            {
                doc.Bookmarks.get_Item(bk).Range.Text = "insert text"; // 插入文本
            }

            doc.SaveAs2(@"F:3.doc", MWord.WdSaveFormat.wdFormatDocument, false);   //另存
            Console.ReadKey();

        }
    }
}