SajetConnect.dll

       [DllImport("SajetConnect.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall, EntryPoint = "SajetTransStart")]
        public static extern bool SajetTransStart();

        [DllImport("SajetConnect.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall, EntryPoint = "SajetTransData")]
        public static extern bool SajetTransData(int f_iCommandNo, StringBuilder f_pData, ref int f_pLen);

        [DllImport("SajetConnect.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall, EntryPoint = "SajetTransClose")]
        public static extern bool SajetTransClose();

        private void button1_Click(object sender, EventArgs e)
        {
            bool rlt1 = SajetTransStart();
            MessageBox.Show(rlt1 ? "成功！" : "失败！");
        }

        private void button2_Click(object sender, EventArgs e)
        {
            string empNo = this.txtEmpNo.Text.Trim();

            int f_iCommandNo;
            StringBuilder f_pData = new StringBuilder();
            f_iCommandNo = 1;
            f_pData.Append(empNo);

            int len = f_pData.Length;

            bool rlt2 = SajetTransData(f_iCommandNo, f_pData, ref len);

            MessageBox.Show(rlt2 ? "成功！" : "失败！");
            this.label1.Text = f_pData.ToString().Substring(0, len);