office文档转Txt文档

代码网络得到，稍作修改，使用从VS2008下取得的dll文件，office2007还支持另为pdf，下面代码运用的就是这种逻辑：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Office.Core;
using Microsoft.Office.Interop.Word;
using Microsoft.Office.Interop.Excel;
using Microsoft.Office.Interop.PowerPoint;
using System.IO;

namespace ConsoleApplication1
{
    public interface FileConvert
    {
        void Convert(string inputfilepath, string outputfilepath);
    }
    public class FileConvertFactory
    {
        private FileConvertFactory() { }
        public static FileConvert CreateFileConvert(string inputfilepath)
        {
            FileConvert fileConvert;
            string extension = Path.GetExtension(inputfilepath);
            switch (extension.ToLower())
            {
                case (".xls"):
                case (".xlsx"):
                    fileConvert = new ExcelFileConvert();
                    break;
                case (".ppt"):
                case (".pptx"):
                    fileConvert = new PPTFileConvert();
                    break;
                case (".doc"):
                case (".docx"):
                default:
                    fileConvert = new DocFileConvert();
                    break;
            }
            return fileConvert;
        }
    }
    public class DocFileConvert : FileConvert
    {
        public void Convert(string inputfilepath, string outputfilepath)
        {
            Microsoft.Office.Interop.Word.ApplicationClass wordApp = new Microsoft.Office.Interop.Word.ApplicationClass();
            object fileName = inputfilepath;
            object missing = Type.Missing;
            //打开文档
            _Document doc = wordApp.Documents.Open(
                ref fileName, ref missing, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing);
            object saveFormat = Microsoft.Office.Interop.Word.WdSaveFormat.wdFormatTextLineBreaks;
            //object saveEncoding = MsoEncoding.msoEncodingUTF8;
            fileName = outputfilepath;
            //保存为TXT文档
            doc.SaveAs(
                ref fileName, ref saveFormat, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing);
            doc.Close(ref missing, ref missing, ref missing);
            wordApp.Quit(ref missing, ref missing, ref missing);
        }
    }

    public class ExcelFileConvert : FileConvert
    {
        public void Convert(string inputfilepath, string outputfilepath)
        {
            Microsoft.Office.Interop.Excel.ApplicationClass wordApp = new Microsoft.Office.Interop.Excel.ApplicationClass();
            object fileName = inputfilepath;
            object missing = Type.Missing;
            Workbook doc = wordApp.Workbooks.Open(
                inputfilepath, missing, missing, missing,
                 missing, missing, missing, missing,
                 missing, missing, missing, missing,
                 missing, missing, missing);
            object saveFormat = Microsoft.Office.Interop.Excel.XlFileFormat.xlUnicodeText;
            object saveResolution = XlSaveConflictResolution.xlLocalSessionChanges;
            doc.SaveAs(
                 outputfilepath, saveFormat, missing, missing,
                 missing, missing, XlSaveAsAccessMode.xlNoChange, saveResolution,
                 missing, missing, missing, missing);
            doc.Close(missing,missing,missing);
            wordApp.Quit();
        }
    }
    public class PPTFileConvert : FileConvert
    {
        public void Convert(string inputfilepath, string outputfilepath)
        {
            Microsoft.Office.Interop.PowerPoint.ApplicationClass wordApp = new Microsoft.Office.Interop.PowerPoint.ApplicationClass();
            object fileName = inputfilepath;
            object missing = Type.Missing;
            Presentation doc = wordApp.Presentations.Open(
                inputfilepath, MsoTriState.msoCTrue, MsoTriState.msoCTrue, MsoTriState.msoFalse);
            object saveFormat = PpSaveAsFileType.ppSaveAsRTF;
            object saveResolution = XlSaveConflictResolution.xlLocalSessionChanges;
            string tempfile = Path.GetDirectoryName(outputfilepath) + DateTime.Now.ToFileTime() + "tmp.rtf";
            //保存为RTF文件
            doc.SaveAs(tempfile, PpSaveAsFileType.ppSaveAsRTF, MsoTriState.msoFalse);
            wordApp.Quit();
            //然后转换为txt文件
            DocFileConvert newConvert = new DocFileConvert();
            newConvert.Convert(tempfile, outputfilepath);
            File.Delete(tempfile);
        }
    }
}