Raw printer helper

RawPrinterHelper.cs

using System;
using System.ComponentModel;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;

internal static class RawPrinterHelper
{
    [StructLayout(LayoutKind.Sequential)]
    private struct DOCINFO
    {
        [MarshalAs(UnmanagedType.LPWStr)]
        public string pDocName;

        [MarshalAs(UnmanagedType.LPWStr)]
        public string pOutputFile;

        [MarshalAs(UnmanagedType.LPWStr)]
        public string pDataType;

        public DOCINFO(string documentName) : this()
        {
            if (string.IsNullOrEmpty(documentName))
            {
                documentName = "RAW Document";
            }

            pDocName = documentName;
            pDataType = "RAW";
        }
    }

    [DllImport("winspool.drv", SetLastError = true, CharSet = CharSet.Unicode, ExactSpelling = false, CallingConvention = CallingConvention.StdCall)]
    private static extern bool OpenPrinter([MarshalAs(UnmanagedType.LPWStr)] string szPrinter, out SafePrinterHandle hPrinter, IntPtr pd);

    [DllImport("winspool.drv", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    private static extern bool ClosePrinter(IntPtr hPrinter);

    [DllImport("winspool.drv", SetLastError = true, CharSet = CharSet.Unicode, ExactSpelling = false, CallingConvention = CallingConvention.StdCall)]
    private static extern bool StartDocPrinter(SafePrinterHandle hPrinter, int level, ref DOCINFO di);

    [DllImport("winspool.drv", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    private static extern bool EndDocPrinter(SafePrinterHandle hPrinter);

    [DllImport("winspool.drv", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    private static extern bool StartPagePrinter(SafePrinterHandle hPrinter);

    [DllImport("winspool.drv", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    private static extern bool EndPagePrinter(SafePrinterHandle hPrinter);

    [DllImport("winspool.drv", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    private static extern bool WritePrinter(SafePrinterHandle hPrinter, [MarshalAs(UnmanagedType.LPStr)] string data, int dwCount, out int dwWritten);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, BestFitMapping = false, ThrowOnUnmappableChar = true)]
    private static extern int FormatMessage(int dwFlags, IntPtr lpSource, int dwMessageId, int dwLanguageId, StringBuilder lpBuffer, int nSize, IntPtr vaListArguments);

    private static string GetErrorMessage(int errorCode)
    {
        var lpBuffer = new StringBuilder(0x200);
        if (FormatMessage(0x3200, IntPtr.Zero, errorCode, 0, lpBuffer, lpBuffer.Capacity, IntPtr.Zero) != 0)
        {
            return lpBuffer.ToString();
        }

        return $"Unknown error: {errorCode}";
    }

    private static void ThrowLastWin32Error(string path = null)
    {
        int errorCode = Marshal.GetLastWin32Error();
        if (errorCode != 0)
        {
            int hr = Marshal.GetHRForLastWin32Error();
            if (0 <= hr) throw new Win32Exception(errorCode);

            switch (errorCode)
            {
                case 2: // File not found
                {
                    if (string.IsNullOrEmpty(path)) throw new FileNotFoundException();
                    throw new FileNotFoundException(null, path);
                }
                case 3: // Directory not found
                {
                    if (string.IsNullOrEmpty(path)) throw new DirectoryNotFoundException();
                    throw new DirectoryNotFoundException($"The directory '{path}' was not found.");
                }
                case 5: // Access denied
                {
                    if (string.IsNullOrEmpty(path)) throw new UnauthorizedAccessException();
                    throw new UnauthorizedAccessException($"Access to the path '{path}' was denied.");
                }
                case 15: // Drive not found
                {
                    if (string.IsNullOrEmpty(path)) throw new DriveNotFoundException();
                    throw new DriveNotFoundException($"Could not find the drive '{path}'. The drive might not be ready or might not be mapped.");
                }
                case 32: // Sharing violation
                {
                    if (string.IsNullOrEmpty(path)) throw new IOException(GetErrorMessage(errorCode), hr);
                    throw new IOException($"The process cannot access the file '{path}' because it is being used by another process.", hr);
                }
                case 80: // File already exists
                {
                    if (!string.IsNullOrEmpty(path))
                    {
                        throw new IOException($"The file '{path}' already exists.", hr);
                    }
                    break;
                }
                case 87: // Invalid parameter
                {
                    throw new IOException(GetErrorMessage(errorCode), hr);
                }
                case 183: // File or directory already exists
                {
                    if (!string.IsNullOrEmpty(path))
                    {
                        throw new IOException($"The file or directory '{path}' already exists.", hr);
                    }
                    break;
                }
                case 206: // Path too long
                {
                    throw new PathTooLongException();
                }
                case 995: // Operation cancelled
                {
                    throw new OperationCanceledException();
                }
                case 1801: // Invalid printer name
                {
                    throw new ArgumentException($"The printer '{path}' was not found.", "printerName");
                }
                default:
                {
                    Marshal.ThrowExceptionForHR(hr);
                    break;
                }
            }
        }
    }

    private sealed class SafePrinterHandle : SafeHandle
    {
        private SafePrinterHandle() : base(IntPtr.Zero, true)
        {
        }

        public override bool IsInvalid
        {
            get { return handle == IntPtr.Zero; }
        }

        protected override bool ReleaseHandle()
        {
            return ClosePrinter(handle);
        }

        public static SafePrinterHandle Open(string printerName)
        {
            SafePrinterHandle result;
            if (!OpenPrinter(printerName, out result, IntPtr.Zero))
            {
                ThrowLastWin32Error(printerName);
            }

            return result;
        }

        public IDisposable StartDocument(string name)
        {
            if (IsInvalid || IsClosed) return null;

            var di = new DOCINFO(name);
            if (!StartDocPrinter(this, 1, ref di))
            {
                ThrowLastWin32Error();
            }

            return new PrinterDocument(this);
        }

        public IDisposable StartPage()
        {
            if (IsInvalid || IsClosed) return null;

            if (!StartPagePrinter(this))
            {
                ThrowLastWin32Error();
            }

            return new PrinterPage(this);
        }

        public void Write(string data)
        {
            if (IsInvalid) throw new InvalidOperationException();
            if (IsClosed) throw new ObjectDisposedException(nameof(SafePrinterHandle));

            int bytesWritten;
            if (!WritePrinter(this, data, data.Length, out bytesWritten))
            {
                ThrowLastWin32Error();
            }
        }
    }

    private sealed class PrinterDocument : IDisposable
    {
        private SafePrinterHandle _printer;

        public PrinterDocument(SafePrinterHandle printer)
        {
            _printer = printer;
        }

        public void Dispose()
        {
            var printer = Interlocked.Exchange(ref _printer, null);
            if (printer != null) EndDocPrinter(printer);
        }
    }

    private sealed class PrinterPage : IDisposable
    {
        private SafePrinterHandle _printer;

        public PrinterPage(SafePrinterHandle printer)
        {
            _printer = printer;
        }

        public void Dispose()
        {
            var printer = Interlocked.Exchange(ref _printer, null);
            if (printer != null) EndPagePrinter(printer);
        }
    }

    /// <summary>
    /// Sends the specified raw string to the printer.
    /// </summary>
    /// <param name="printerName">
    /// The name of the printer which receives the string.
    /// </param>
    /// <param name="valueToSend">
    /// The string to send.
    /// </param>
    /// <param name="documentName">
    /// The document name to use, if any.
    /// </param>
    /// <exception cref="ArgumentNullException">
    /// <para><paramref name="printerName"/> is <see langword="null"/> or <see cref="string.Empty"/>.</para>
    /// <para>-or-</para>
    /// <para><paramref name="valueToSend"/> is <see langword="null"/> or <see cref="string.Empty"/>.</para>
    /// </exception>
    /// <exception cref="ArgumentException">
    /// <para>The specified printer was not found.</para>
    /// </exception>
    /// <exception cref="Win32Exception">
    /// There was an error sending the data to the printer.
    /// </exception>
    public static void SendStringToPrinter(string printerName, string valueToSend, string documentName)
    {
        if (string.IsNullOrWhiteSpace(printerName)) throw new ArgumentNullException(nameof(printerName));
        if (string.IsNullOrEmpty(valueToSend)) throw new ArgumentNullException(nameof(valueToSend));

        using (var printer = SafePrinterHandle.Open(printerName))
        using (printer.StartDocument(documentName))
        using (printer.StartPage())
        {
            printer.Write(valueToSend);
        }
    }
}

what is the correct way to print a picture using this? what conditions should have the picture?thanks

@Dager-dm This class was designed specifically for sending raw ZPL strings to a label printer. The WritePrinter function seems to support other formats, such as PCL or PostScript, but I've never had to do that.

It would probably be easier to use the PrintDocument class instead.