求CSDN的各位大神帮我看看

   private void btnPrint_Click(object sender, EventArgs e)
        {
            try
            {
                //以tbJB这个文本框的值来查找脚本文件
                string strline;
                FileStream afile = new FileStream("" + tbJB.Text + "", FileMode.Open);
                //MessageBox.Show("当前打开的文件"+tbJB.Text);
                StreamWriter sw = new StreamWriter(afile);                //读取脚本文件并用界面的值替换脚本中对应的变量
                StreamReader sr = new StreamReader(afile);
                strline = sr.ReadToEnd();
                sw.Close();
                string a = strline;                a = a.Replace("$QSSN$", this.tbSN.Text);
                a = a.Replace("$FLASH$", this.tbFlash.Text);
                a = a.Replace("$PD$", this.cbPD.Text);
                a = a.Replace("$JZ$", this.tbJZ.Text);
                a = a.Replace("$SL$", this.tbSL.Text);
                //a = a.Replace("$HW$", this.textBox2.Text);
                //a = a.Replace("$SW$", this.textBox4.Text);
                //a = a.Replace("$WEEK$", this.label10.Text);
                //a = a.Replace("$YEAR$", DateTime.Now.Year.ToString().Remove(0, 2));                FileStream bfile = new FileStream("label17.txt", FileMode.Create);
                StreamWriter ssw = new StreamWriter(bfile);
                ssw.WriteLine(a);                ssw.Close();                //把脚本推送到打印机
                Process p = new Process();                p.StartInfo.FileName = "cmd.exe";                p.StartInfo.UseShellExecute = false;                p.StartInfo.RedirectStandardInput = true;                p.StartInfo.RedirectStandardOutput = true;                p.StartInfo.RedirectStandardError = true;                p.StartInfo.CreateNoWindow = true;                string pingrst;
                p.Start();                p.StandardInput.WriteLine("copy label.txt lpt1");                p.StandardInput.WriteLine("exit");                string strRst = p.StandardOutput.ReadToEnd();                if (strRst.IndexOf("(0% loss)") != -1)
                {
                    pingrst = "连接";
                }                else if (strRst.IndexOf("Destination host unreachable.") != -1)
                {
                    pingrst = "无法到达目的主机";
                }                else if (strRst.IndexOf("Request timed out.") != -1)
                {
                    pingrst = "超时";
                }
                else if (strRst.IndexOf("Unknown host") != -1)
                {
                    pingrst = "无法解析主机";
                }
                else
                {
                    pingrst = strRst;
                }
                p.Close();
                MessageBox.Show("打印完成！");
            }
            catch (IOException ex)
            {
                MessageBox.Show(ex.ToString().Trim());
            }
        }
这是我写的打印，但是现在有点问题请教各位 因为想在有两台打印我都要使用 但是 我写的 只能通过其中一台打印机打印，我请各位大神帮我改造下代码 让这段代码可以通过不同的打印端口打印  两台打印机的端口 分别为LPT1  LPT3