private FileStream fs = null;        [DllImport("kernel32.dll", CharSet = CharSet.Auto)]//调用系统API打印函数        public static extern IntPtr CreateFile        (            string FileName,          // file name            uint DesiredAccess,       // access mode            uint ShareMode,           // share mode            uint SecurityAttributes,  // Security Attributes            uint CreationDisposition, // how to create            uint FlagsAndAttributes,  // file attributes            string hTemplateFile      // handle to template file        );        /// <summary>        /// 打印小票        /// </summary>        /// <param name="msg"></param>        /// <returns></returns>        public string PrintMsg(string PosPort, string msg, bool isOpenMoneyBox)        {            try            {                IntPtr iHandle = CreateFile(PosPort, 0x40000000, 0, 0, 3, 0, null);                if (iHandle.ToInt32() == -1)                {                    return "票机连接失败.或者端口号错误.请测试打印机是否正常!";                }                else                {                    try                    {                        fs = new FileStream(iHandle, FileAccess.ReadWrite);                        StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.Default);   //写数据                           sw.WriteLine(msg);                        //开启钱箱                        if (isOpenMoneyBox)                        {                            sw.Write(((char)27).ToString() + "p" + ((char)0).ToString() + ((char)60).ToString() + ((char)255).ToString());                        }                        sw.Flush();                        sw.Close();                        fs.Close();                        return "";                    }                    catch (Exception ex)                    {                        return ex.InnerException == null ? ex.Message : ex.InnerException.Message;                    }                }            }            catch (Exception exp)            {                return "TPL或者COM口连接失败！";            }        }