如何给条码增加预览功能
我最近调用TSC公司的TSClib.dll能打印出条码，但是不懂实现条码预览功能，我把全部代码帖出来，请大家并我看看，怎么才能实现条码预览功能。
programs.cs

using System;
using System.Collections.Generic;
using System.Windows.Forms;



using System.Runtime.InteropServices;
public class TSCLIB_DLL
{
  [DllImport("TSCLIB.dll", EntryPoint = "about")]
  public static extern int about();

  [DllImport("TSCLIB.dll", EntryPoint = "openport")]
  public static extern int openport(string printername);

  [DllImport("TSCLIB.dll", EntryPoint = "barcode")]
  public static extern int barcode(string x, string y, string type,
  string height, string readable, string rotation, string narrow, string wide, string code);

  [DllImport("TSCLIB.dll", EntryPoint = "clearbuffer")]
  public static extern int clearbuffer();

  [DllImport("TSCLIB.dll", EntryPoint = "closeport")]
  public static extern int closeport();

  [DllImport("TSCLIB.dll", EntryPoint = "downloadpcx")]
  public static extern int downloadpcx(string filename, string image_name);

  [DllImport("TSCLIB.dll", EntryPoint = "formfeed")]
  public static extern int formfeed();

  [DllImport("TSCLIB.dll", EntryPoint = "nobackfeed")]
  public static extern int nobackfeed();

  [DllImport("TSCLIB.dll", EntryPoint = "printerfont")]
  public static extern int printerfont(string x, string y, string fonttype,string rotation, string xmul, string ymul,string text);

  [DllImport("TSCLIB.dll", EntryPoint = "printlabel")]
  public static extern int printlabel(string set, string copy);

  [DllImport("TSCLIB.dll", EntryPoint = "sendcommand")]
  public static extern int sendcommand(string printercommand);

  [DllImport("TSCLIB.dll", EntryPoint = "setup")]
  public static extern int setup(string width, string height,string speed, string density,string sensor, string vertical,string offset);

  [DllImport("TSCLIB.dll", EntryPoint = "windowsfont")]
  public static extern int windowsfont(int x, int y, int fontheight,int rotation, int fontstyle, int fontunderline,string szFaceName, string content);

}




namespace 条码打印
{
  static class Program
  {
  /// <summary>
  /// 应用程序的主入口点。
  /// </summary>
  [STAThread]
  static void Main()
  {
  Application.EnableVisualStyles();
  Application.SetCompatibleTextRenderingDefault(false);
  Application.Run(new Form1());
  }
  }
}





Form1.cs


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Printing;
using System.Text;
using System.Windows.Forms;

namespace 条码打印
{
  public partial class Form1 : Form
  {
  public Form1()
  {
  InitializeComponent();
  }




   

  private void button1_Click(object sender, EventArgs e)
  {
  TSCLIB_DLL.openport("TSC TTP-342