รบกวนที่ ครับ เรื่อง CashDrawer สั้งเปิด จากโปรแกรม

 public class CashDrawerClass
    {
        CashDrawer myCashDrawer;
        PosExplorer explorer;

        public CashDrawerClass()
        {
            
            explorer = new PosExplorer();
            DeviceInfo ObjDevicesInfo = explorer.GetDevice("CashDrawer");
            myCashDrawer = explorer.CreateInstance(ObjDevicesInfo);  //ตอนrun มัน Error ตรงนี้ครับ
            
        }

        public void OpenCashDrawer()
        {
            myCashDrawer.Open();
            myCashDrawer.Claim(1000);
            myCashDrawer.DeviceEnabled = true;
            myCashDrawer.OpenDrawer();
            myCashDrawer.DeviceEnabled = false;
            myCashDrawer.Release();
            myCashDrawer.Close();
        }
    }

public static bool OpenCashDrawer1( string szPrinterName)
            {
                //27,112,48,55,121
            Int32 dwError = 0, dwWritten = 0;
            IntPtr hPrinter = new IntPtr(0);
            DOCINFOA di = new DOCINFOA();            
            bool bSuccess = false;
            di.pDocName = "OpenDrawer";
            di.pDataType = "RAW";
            if( OpenPrinter( szPrinterName, out hPrinter, 0 ) )
                {
                if( StartDocPrinter(hPrinter, 1, di) )
                    {
                    if( StartPagePrinter(hPrinter) )
                        {
                        int nLength;
                        byte[] DrawerOpen = new byte[] { 07 };
                        nLength = DrawerOpen.Length;
                        IntPtr p = Marshal.AllocCoTaskMem(nLength);
                        Marshal.Copy(DrawerOpen, 0, p, nLength);
                        bSuccess = WritePrinter(hPrinter, p, DrawerOpen.Length, out dwWritten);
                        EndPagePrinter(hPrinter);
                        Marshal.FreeCoTaskMem(p);
                        }
                    EndDocPrinter(hPrinter);
                    }
                ClosePrinter(hPrinter);
                }
            if( bSuccess == false )
                {
                dwError = GetLastError();
                }
            return bSuccess;
            }