C#读IC卡

[DllImport("sdtapi.dll")]
        static extern IntPtr InitComm(IntPtr iPort);

        [DllImport("sdtapi.dll")]
        static extern IntPtr CloseComm();

        [DllImport("sdtapi.dll")]
        static extern IntPtr Authenticate();

        [DllImport("sdtapi.dll")]
        static extern IntPtr Routon_IC_HL_ReadCardSN(StringBuilder SN);

        [DllImport("sdtapi.dll")]
        static extern IntPtr HID_BeepLED(bool BeepON, bool LEDON, Int32 duration);

int port = 1001;
            IntPtr ret = InitComm(new IntPtr(port));
            if (ret.ToInt32() > 0)
            {
                ret = Authenticate();
                if (ret.ToInt32() > 0)
                {
                    //身份证
                }
                else
                {
                    StringBuilder msg = new StringBuilder();
                    ret = Routon_IC_HL_ReadCardSN(msg);
                    label1.Text="卡号：" + msg;
                    HID_BeepLED(true, true, 10);
                }
                CloseComm();
            }