自己琢磨的，看了打印机的指令自己写的。共享出来，免得大家又去看烦人的指令

    public class EpsopnPrinter
    {

        //打印文字（端口号 字符）
        public static string PrintString(int Port, string val)
        {
            System.IO.Ports.SerialPort sp = new System.IO.Ports.SerialPort();
            sp.PortName = "COM" + Port.ToString();
            try
            {
                sp.Open();
            }
            catch
            {
                return "端口被占用";
            }
            List<byte> data = new List<byte>();
            string[] lines = val.Split('\n');
            for (int i = 0; i < lines.Length; i++)
            {
                byte[] content = System.Text.Encoding.Default.GetBytes(lines[i].Replace("\r", ""));
                byte[] wapbt ={ 0x0a };
                data.AddRange(content);
                data.AddRange(wapbt);
            }
            byte[] cutbt={0x1d,0x56,0x42,0x11};
            data.AddRange(cutbt);
            byte[] databt = data.ToArray();
            sp.Write(databt, 0, databt.Length);
            sp.Close();
            return null;
        }

//测试打印机是否接在这个端口
        public static bool PrintTest(int Port)
        {
            System.IO.Ports.SerialPort sp = new System.IO.Ports.SerialPort();
            sp.PortName = "COM" + Port.ToString();
            sp.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(sp_DataReceived);
            try
            {
                sp.Open();
            }
            catch
            {
                return false;
            }
            Recived = false;
            byte[] testbt={0x1D,0x49,0x01};
            sp.Write(testbt, 0, testbt.Length);
            System.Threading.Thread.Sleep(100);
            sp.Close();
            return Recived;
        }

        static bool Recived = false;
        static void sp_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
        {
            Recived = true;
        }
    }