c# 读卡器 读取数据

        [DllImport("MWIC_32.dll", EntryPoint = "srd_4442")]
        private static extern int srd_4442(int icdev, int Offset, int le,int databuffer);

 private void button3_Click(object sender, EventArgs e)
        {
            int icdev;

            icdev = auto_init(1, 9600);
            int srd;

            //srd = srd_4442(icdev, 127, 2, 1);
            srd = srd_4442(icdev, 32, 1, 2);
            textBox4.Text = srd.ToString();
        }

怎么确定 这个Offset偏移地址。可以读取固定位置的数据。并且成为字符串！