C#操作txt文件,进行清空添加操作的小例子

//把txt清空
            filestream stream = file.open(adr,filemode.openorcreate,fileaccess.write);
            stream.seek(0, seekorigin.begin);
            stream.setlength(0);
            stream.close();
            //向txt里面追加信息
            streamwriter sw = new streamwriter(adr,true,encoding.getencoding("gb2312"));
            sw.writeline(str);
            sw.flush();
            sw.close();