//定义Word对象
            Microsoft.Office.Interop.Word.ApplicationClass wordApp = new Microsoft.Office.Interop.Word.ApplicationClass();

            //要转换的文件名
            object fileName="d:\\test.doc";

            //默认值
            object miss = Missing.Value;

            //打开要转换的 DOC 文件
            Microsoft.Office.Interop.Word.DocumentClass doc=(Microsoft.Office.Interop.Word.DocumentClass) wordApp.Documents.Open(ref fileName,ref miss,ref miss,
                ref miss,ref miss,
                ref miss,ref miss,
                ref miss,ref miss,
                ref miss, ref miss, ref miss,
                ref miss,ref miss,
                ref miss,ref miss);

            //转换后的文件名
            fileName = "d:\\testDoc.txt";

            //保存的文件格式，这里 2 指 文本文件
            object saveFormat=2;

            //按文本文件保存
            doc.SaveAs(ref fileName, ref saveFormat, ref miss, ref miss,
                ref miss, ref miss, ref miss,
                ref miss, ref miss, ref miss,
                ref miss, ref miss, ref miss,
                ref miss, ref miss, ref miss);

            //关闭是否保存文件，这里为不保存
            object changes = false;

            //关闭文件
            doc.Close(ref changes, ref miss, ref miss);

            //退出 Word 应用程序
            wordApp.Quit(ref changes, ref miss, ref miss);