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ReadPrinter function always return false in c# RRS feed

  • Question

  • Please look into the code and let me know why always the read printer method is returning false ? do i need to call writeprinter first and then readprinter ? i just want to get printer status by sending a ZPL command and then receiving the response. 

    Most likely i may be giving it the wrong parameters but can some tell me how to implement it ? reference to the function im trying to use is as below: 

    https://msdn.microsoft.com/en-us/library/windows/desktop/dd162895(v=vs.85).aspx

    this is how im doing it (Please correct me if im doing something wrong:

            [DllImport("winspool.Drv", EntryPoint = "ReadPrinter", SetLastError = true, ExactSpelling = true, CallingConvention =                     CallingConvention.StdCall)]
            public static extern Boolean ReadPrinter(IntPtr hPrinter, out StringBuilder data, Int32 cbBuf, out IntPtr pNoBytesRead);

             public static Boolean ReadBytesFromPrinter(String szPrinterName, string command)
            {
                Int32 dwError = 0; IntPtr dwWritten;
                IntPtr hPrinter = new IntPtr(0);
                DOCINFOA di = new DOCINFOA();
                Boolean bSuccess = false; // Assume failure unless you specifically succeed.
                
                
                di.pDocName = "SendBytesToPrinter";
                di.pDataType = "RAW";


                // Open the printer.
                if (OpenPrinter(szPrinterName.Normalize(), out hPrinter, IntPtr.Zero))
                {
                    // Start a document.
                    if (StartDocPrinter(hPrinter, 1, di))
                    {
                        // Start a page.
                        if (StartPagePrinter(hPrinter))
                        {
                            Int32 maxRead = 256;
                            StringBuilder sbData = new StringBuilder(maxRead);
                          
                            //Read Data      
                            bSuccess = 
                            bSuccess = ReadPrinter(hPrinter,out  command, maxRead, out dwWritten);
                            data = sbData.ToString();

                            EndPagePrinter(hPrinter);

                            EndDocPrinter(hPrinter);

                            ClosePrinter(hPrinter);
                        }

                    }
                }
                // If you did not succeed, GetLastError may give more information
                // about why not.
                if (bSuccess == false)
                {
                    dwError = Marshal.GetLastWin32Error();
                    data = null;
                }

                return bSuccess;
            }

    Friday, August 5, 2016 9:19 AM

Answers

  • Hi KhawajaHassan,

    Please try to use the following code and check if it works for you

    [DllImport("winspool.Drv", EntryPoint = "ReadPrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
         static extern bool ReadPrinter(IntPtr hPrinter, IntPtr pBuf, int cbBuf, out int pNoBytesRead);

    For more information, please refer to:

    http://www.pinvoke.net/default.aspx/winspool.ReadPrinter

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    Best regards,

    Cole Wu


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    Monday, August 8, 2016 8:33 AM
    Moderator