C# implements scanning the QR code and printing the scan gun (example code)

using System;
using ;
using ;
using ;
using ;
using ;
namespace am_sign
{
 class BardCodeHooK
 {
  public delegate void BardCodeDeletegate(BarCodes barCode);
  public event BardCodeDeletegate BarCodeEvent;
  public struct BarCodes
  {
   public int VirtKey;//Is it virtual   public int ScanCode;//Scan the code   public string KeyName;//Key name   public uint Ascll;//Ascll
   public char Chr;//character   public string BarCode;//Barcode information   public bool IsValid;//Is the barcode valid   public DateTime Time;//Scan time  }
  private struct EventMsg
  {
   public int message;
   public int paramL;
   public int paramH;
   public int Time;
   public int hwnd;
  }
  [DllImport("", CharSet = , CallingConvention = )]
  private static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);
  [DllImport("", CharSet = , CallingConvention = )]
  private static extern bool UnhookWindowsHookEx(int idHook);
  [DllImport("", CharSet = , CallingConvention = )]
  private static extern int CallNextHookEx(int idHook, int nCode, Int32 wParam, IntPtr lParam);
  [DllImport("user32", EntryPoint = "GetKeyNameText")]
  private static extern int GetKeyNameText(int IParam, StringBuilder lpBuffer, int nSize);
  [DllImport("user32", EntryPoint = "GetKeyboardState")]
  private static extern int GetKeyboardState(byte[] pbKeyState);
  [DllImport("user32", EntryPoint = "ToAscii")]
  private static extern bool ToAscii(int VirtualKey, int ScanCode, byte[] lpKeySate, ref uint lpChar, int uFlags);
  delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);
  BarCodes barCode = new BarCodes();
  int hKeyboardHook = 0;
  string strBarCode = "";
  private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
  {
   if (nCode == 0)
   {
    EventMsg msg = (EventMsg)(lParam, typeof(EventMsg));
    if (wParam == 0x100)//WM_KEYDOWN=0x100
    {
      =  & 0xff;//Is it virtual      =  & 0xff;//Scan the code     StringBuilder strKeyName = new StringBuilder(225);
     if (GetKeyNameText( * 65536, strKeyName, 255) > 0)
     {
       = ().Trim(new char[] { ' ', '\0' });
     }
     else
     {
       = "";
     }
     byte[] kbArray = new byte[256];
     uint uKey = 0;
     GetKeyboardState(kbArray);
     if (ToAscii(, , kbArray, ref uKey, 0))
     {
       = uKey;
       = (uKey);
     }
     TimeSpan ts = ();
     if ( > 50)
     {
      strBarCode = ();
     }
     else
     {
      if (( & 0xff) == 13 &&  > 3)
      {
        = strBarCode;
        = true;
      }
      strBarCode += ();
     }
      = ;
     if (BarCodeEvent != null) BarCodeEvent(barCode);//Trigger event      = false;
    }
   }
   return CallNextHookEx(hKeyboardHook, nCode, wParam, lParam);
  }
  //Installing the hook  public bool Start()
  {
   if (hKeyboardHook == 0)
   {
    //WH_KEYBOARD_LL=13
    hKeyboardHook = SetWindowsHookEx(13, new HookProc(KeyboardHookProc), (().GetModules()[0]), 0);
   }
   return (hKeyboardHook != 0);
  }
  //Unload hook  public bool Stop()
  {
   if (hKeyboardHook != 0)
   {
    return UnhookWindowsHookEx(hKeyboardHook);
   }
   return true;
  }
 }
}

 BardCodeHooK BarCode = new BardCodeHooK();
  public Form1()
  {
   InitializeComponent();
    += new (BarCode_BarCodeEvent);
  }
  string value = ""; //value is the content obtained by the code scan gun, ending with Enter  private delegate void ShowInfoDelegate( barCode);
  private void ShowInfo( barCode)
  {
   if ()
   {
    (new ShowInfoDelegate(ShowInfo), new object[] { barCode });
   }
   else
   {
    if (("Enter"))
    {
     hook_KeyDown(value);
     value = "";
    }
    else
    {
     value += ();
    }
   }
  }
  void BarCode_BarCodeEvent( barCode)
  {
   ShowInfo(barCode);
  }

using ;
namespace am_sign
{
 class TSCLIB_DLL
 {
  [DllImport("", EntryPoint = "about")]
  public static extern int about();
  [DllImport("", EntryPoint = "openport")]
  public static extern int openport(string printername);
  [DllImport("", 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("", EntryPoint = "clearbuffer")]
  public static extern int clearbuffer();
  [DllImport("", EntryPoint = "closeport")]
  public static extern int closeport();
  [DllImport("", EntryPoint = "downloadpcx")]
  public static extern int downloadpcx(string filename, string image_name);
  [DllImport("", EntryPoint = "formfeed")]
  public static extern int formfeed();
  [DllImport("", EntryPoint = "nobackfeed")]
  public static extern int nobackfeed();
  [DllImport("", EntryPoint = "printerfont")]
  public static extern int printerfont(string x, string y, string fonttype,
       string rotation, string xmul, string ymul,
       string text);
  [DllImport("", EntryPoint = "printlabel")]
  public static extern int printlabel(string set, string copy);
  [DllImport("", EntryPoint = "sendcommand")]
  public static extern int sendcommand(string printercommand);
  [DllImport("", EntryPoint = "setup")]
  public static extern int setup(string width, string height,
      string speed, string density,
      string sensor, string vertical,
      string offset);
  [DllImport("", EntryPoint = "windowsfont")]
  public static extern int windowsfont(int x, int y, int fontheight,
   int rotation, int fontstyle, int fontunderline,
       string szFaceName, string content);
  //Open the printer port and make relevant settings  public static void openportExt()
  {
   TSCLIB_DLL.openport("Gprinter GP-3120TU");//Look for the printer port   TSCLIB_DLL.sendcommand("SIZE 70 mm,50 mm");//Set the barcode size   TSCLIB_DLL.sendcommand("GAP 2 mm,0");//Set the barcode gap   TSCLIB_DLL.sendcommand("SPEED 5");//Set the printing speed   TSCLIB_DLL.sendcommand("DENSITY 8");//Set the ink concentration   TSCLIB_DLL.sendcommand("DERECTION 1");//Set relative starting point   TSCLIB_DLL.sendcommand("REFERENCE 3 mm,3 mm");//Set offset border   TSCLIB_DLL.sendcommand("CLS");//Clear the memory (clear the last printed memory each time you print a new barcode)  }
  //Print in QR code  public static void printVehicleCode(string name, string department, string seat_area,string qrcode)
  {
   TSCLIB_DLL.sendcommand("CLS");//The last print memory needs to be cleared   TSCLIB_DLL.sendcommand("QRCODE 207,180,L,6,A,0,M2,S3,\"" + qrcode + "\"");
   TSCLIB_DLL.windowsfont(200, 30, 60, 0, 2, 0, "Microsoft YaHei", name);
   TSCLIB_DLL.windowsfont(210, 100, 30, 0, 0, 0, "Microsoft YaHei", department);
   TSCLIB_DLL.windowsfont(20, 320, 40, 0, 0, 0, "Microsoft YaHei", seat_area);
   TSCLIB_DLL.printlabel("1", "1");
  }
  //Close the printer port  public static void closeportExt()
  {
   TSCLIB_DLL.closeport();
  }
 }
}

 TSCLIB_DLL.openportExt();           //Open specified printer driver
 TSCLIB_DLL.printVehicleCode(“test”, “test”, "test", “QR code content”);
 TSCLIB_DLL.closeport();