C#使用Twain协议实现扫描仪连续扫描功能

ScanCommon  scan = new RS_ScanCommon(fileName, this.Handle);
    scan.PassDataBetweenForm += new RS_ScanCommon.PassDataBetweenFormHandler(scan_PassDataBetweenForm);
    //是否连续扫描
    scan.bContinuousScan = true;
    scan.dtRow = dtRow;
    this.Enabled = false;
    scan.StartScan();

// 添加一个委托 
        public delegate void PassDataBetweenFormHandler(object sender, PassDataEventArgs e);
        // 添加一个PassDataBetweenFormHandler 类型的事件 
        public event PassDataBetweenFormHandler PassDataBetweenForm;
      public ScanCommon(string fileName, IntPtr Handle)
        {
            this.fileName = fileName;
            this.Handle = Handle;
            //扫描初始化（默认使用TWAIN方式进行连接）
            tw = new Twain();
            tw.Init(Handle, out rc);
            //tw.Select();
        }
       //启动扫描
       public void StartScan()
        {
            if (rc != TwRC.Success)
            {
                MessageBox.Show("设备初始化失败，请检查硬件及驱动！");
            }
            else
            {               
                string path = "XXX路径" + "\\ScannerFile\\" + frmName;
                if (Scanning(path) == false)
                {                  
                        MessageBox.Show("设备未找到或设备不支持TWAIN组件，无法自动创建扫描任务。") ;                    
                 
                   //回调主窗口
                    PassDataEventArgs args = new PassDataEventArgs("exit");
                    PassDataBetweenForm(this, args);
                    GC.Collect();
                }
            }
        }

#region 扫描的一些方法
 private bool Scanning(string filePath)
 {           
     if (!msgfilter)
     {
         msgfilter = true;
         Application.AddMessageFilter(this);
     }
     ScanPath = filePath;
     return tw.Acquire(ref strScanErrorMessage, bContinuousScan);
 }
 
 /// <summary>
 /// 保存图片
 /// </summary>
 /// <param name="dibhandp"></param>
 private void ImageSave(IntPtr dibhandp)
 {
     bmprect = new Rectangle(0, 0, 0, 0);
     if (dibhandp != IntPtr.Zero) dibhand = dibhandp;
     bmpptr = GlobalLock(dibhand);
     pixptr = GetPixelInfo(bmpptr);
 }
 
 public void EndingScan()
 {
     if (msgfilter)
     {
         tw.Finish();
         RemoveMessageFilter(this);
         msgfilter = false;
     }
 }
 
 public static void RemoveMessageFilter(IMessageFilter value)
 {
     Application.RemoveMessageFilter(value);
 }
 #endregion

//此行代码是连续扫描
TwCapability cap = new TwCapability(TwCap.XferCount, -1);

/// <summary>
/// 启动扫描
/// </summary>
/// <param name="strScanErrorMessage"></param>
/// <returns></returns>       
public bool Acquire(ref string strScanErrorMessage, bool MultiScan)
{
    try
    {
        TwRC rc;
        CloseSrc();
        if (appid.Id == IntPtr.Zero)
        {
            Init(hwnd, out rc);
            if (appid.Id == IntPtr.Zero)
                strScanErrorMessage = "未找到扫描仪设备，请查看是否安装扫描仪驱动！";
            return false;
        }
        rc = DSMident(appid, IntPtr.Zero, TwDG.Control, TwDAT.Identity, TwMSG.OpenDS, srcds);
        if (rc != TwRC.Success)
        {
            strScanErrorMessage = "未找到扫描仪设备";
            return false;
        }
 
        if (MultiScan)
        {
            //如果是连续扫描
            TwCapability cap = new TwCapability(TwCap.XferCount, -1);
            rc = DScap(appid, srcds, TwDG.Control, TwDAT.Capability, TwMSG.Set, cap);
        }
        else
        {
            //否则只扫描一张
            TwCapability cap = new TwCapability(TwCap.XferCount, 1);
            rc = DScap(appid, srcds, TwDG.Control, TwDAT.Capability, TwMSG.Set, cap);
        }
 
        if (rc != TwRC.Success)
        {
            strScanErrorMessage = "未找到扫描仪设备";
            CloseSrc();
            return false;
        }
 
        TwUserInterface guif = new TwUserInterface();
        guif.ShowUI = 1;
        guif.ModalUI = 1;
        guif.ParentHand = hwnd;
        rc = DSuserif(appid, srcds, TwDG.Control, TwDAT.UserInterface, TwMSG.EnableDS, guif);
        if (rc != TwRC.Success)
        {
            strScanErrorMessage = "扫描仪中没有纸";
            CloseSrc();
            GC.Collect();
            return false;
        }
    }
    catch (Exception e)
    {
        strScanErrorMessage = e.Message;
        GC.Collect();
        return false;
    }
    GC.Collect();
    return true;
}

private void scan_PassDataBetweenForm(object sender, PassDataEventArgs e)
  {
      if (e.EventStr == "exit")
      {
          this.Cursor = Cursors.WaitCursor;
          frm.dtRow = this.dtRow;
           
          //处理图片的一些方法....
           
          this.Enabled = true;
          this.Cursor = Cursors.Default;
          GC.Collect();
      }
  }