Zebra Printer C# code to print barcode label

Here's a Microsoft class for sending bytes to printer. It's ready to use out of the box:

    using System;
using System.IO;
using System.Runtime.InteropServices;

public class RawPrinterHelper
{
    // Structure and API declarions:
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    public class DOCINFOA
    {
        [MarshalAs(UnmanagedType.LPStr)]
        public string pDocName;
        [MarshalAs(UnmanagedType.LPStr)]
        public string pOutputFile;
        [MarshalAs(UnmanagedType.LPStr)]
        public string pDataType;
    }
    [DllImport("winspool.Drv", EntryPoint = "OpenPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool OpenPrinter([MarshalAs(UnmanagedType.LPStr)] string szPrinter, out IntPtr hPrinter, IntPtr pd);

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

    [DllImport("winspool.Drv", EntryPoint = "StartDocPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool StartDocPrinter(IntPtr hPrinter, int level, [In, MarshalAs(UnmanagedType.LPStruct)] DOCINFOA di);

    [DllImport("winspool.Drv", EntryPoint = "EndDocPrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool EndDocPrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint = "StartPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool StartPagePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint = "EndPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool EndPagePrinter(IntPtr hPrinter);

    [DllImport("winspool.Drv", EntryPoint = "WritePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
    public static extern bool WritePrinter(IntPtr hPrinter, IntPtr pBytes, int dwCount, out int dwWritten);

    // SendBytesToPrinter()
    // When the function is given a printer name and an unmanaged array
    // of bytes, the function sends those bytes to the print queue.
    // Returns true on success, false on failure.
    public static bool SendBytesToPrinter(string szPrinterName, IntPtr pBytes, int dwCount)
    {
        int dwError = 0, dwWritten = 0;
        IntPtr hPrinter = new IntPtr(0);
        DOCINFOA di = new DOCINFOA();
        bool bSuccess = false; // Assume failure unless you specifically succeed.
        di.pDocName = "My C#.NET RAW Document";
        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))
                {
                    // Write your bytes.
                    bSuccess = WritePrinter(hPrinter, pBytes, dwCount, out dwWritten);
                    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();
        }
        return bSuccess;
    }

    public static bool SendFileToPrinter(string szPrinterName, string szFileName)
    {
        // Open the file.
        FileStream fs = new FileStream(szFileName, FileMode.Open);
        // Create a BinaryReader on the file.
        BinaryReader br = new BinaryReader(fs);
        // Dim an array of bytes big enough to hold the file's contents.
        byte[] bytes = new Byte[fs.Length];
        bool bSuccess = false;
        // Your unmanaged pointer.
        IntPtr pUnmanagedBytes = new IntPtr(0);
        int nLength;

        nLength = Convert.ToInt32(fs.Length);
        // Read the contents of the file into the array.
        bytes = br.ReadBytes(nLength);
        // Allocate some unmanaged memory for those bytes.
        pUnmanagedBytes = Marshal.AllocCoTaskMem(nLength);
        // Copy the managed byte array into the unmanaged array.
        Marshal.Copy(bytes, 0, pUnmanagedBytes, nLength);
        // Send the unmanaged bytes to the printer.
        bSuccess = SendBytesToPrinter(szPrinterName, pUnmanagedBytes, nLength);
        // Free the unmanaged memory that you allocated earlier.
        Marshal.FreeCoTaskMem(pUnmanagedBytes);
        return bSuccess;
    }

    public static bool SendStringToPrinter(string szPrinterName, string szString)
    {
        IntPtr pBytes;
        int dwCount;

        // How many characters are in the string?
        // Fix from Nicholas Piasecki:
        // dwCount = szString.Length;
        dwCount = (szString.Length + 1) * Marshal.SystemMaxDBCSCharSize;

        // Assume that the printer is expecting ANSI text, and then convert
        // the string to ANSI text.
        pBytes = Marshal.StringToCoTaskMemAnsi(szString);
        // Send the converted ANSI string to the printer.
        SendBytesToPrinter(szPrinterName, pBytes, dwCount);
        Marshal.FreeCoTaskMem(pBytes);
        return true;
    }
}

After that Format your ZPL request and send it to the Print Class:

     StringBuilder ZplBuilder = new StringBuilder();

    // Exemple ZPL String

                        ZplBuilder.Append("^XA");   //Start ZPL
                        ZplBuilder.Append("^FO320,42^APN,48,48^FD").Append(DateTime.Now.Date.ToString("dd/MM/yyyy")).Append("^FS");
ZplBuilder.Append("^FO0,304^GB720,168,1^FS");
ZplBuilder.Append("^FO0,306^GD720,166,1,B,L^FS");
ZplBuilder.Append("^FO0,306^GD720,166,1,B,R^FS");
ZplBuilder.Append("^XZ"); 
    // End ZPL

string ZplString = ZplBuilder.ToString();

MemoryStream lmemStream = new MemoryStream();

StreamWriter lstreamWriter = new StreamWriter(lmemStream);
lstreamWriter.Write(ZplString);
lstreamWriter.Flush();
lmemStream.Position = 0;

byte[] byteArray = lmemStream.ToArray();

IntPtr cpUnmanagedBytes = new IntPtr(0);
int cnLength = byteArray.Length;
cpUnmanagedBytes = Marshal.AllocCoTaskMem(cnLength);
Marshal.Copy(byteArray, 0, cpUnmanagedBytes, cnLength);

RawPrinterHelper.SendBytesToPrinter("Intermec PC43d (203 dpi)", cpUnmanagedBytes, cnLength);
Marshal.FreeCoTaskMem(cpUnmanagedBytes);

It works fine on an intermec Printec with ZPL Protocel.

I hope this will help.

This is what we do.

namespace SafeHandles
{
    public class PrinterSafeHandle : global::Microsoft.Win32.SafeHandles.SafeHandleZeroOrMinusOneIsInvalid
    {
        [DllImport("winspool.drv", CharSet=CharSet.Auto, SetLastError=true)]
        private static extern bool OpenPrinter(string pPrinterName, out IntPtr phPrinter, IntPtr pDefault);

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

        public PrinterSafeHandle(string PrinterName) : base(true)
        {
            if (!OpenPrinter(PrinterName, out this.handle, IntPtr.Zero))
            {
                throw new System.ComponentModel.Win32Exception();
            }
        }

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

[DllImport("winspool.drv", CharSet=CharSet.Auto, SetLastError=true)]
private static extern bool WritePrinter (SafeHandles.PrinterSafeHandle hPrinter, [In, MarshalAs(UnmanagedType.LPArray)] byte[] pBuf, int cdBuf, out int pcWritten);

[DllImport("winspool.drv", CharSet=CharSet.Auto, SetLastError=true)]
private static extern bool WritePrinter (SafeHandles.PrinterSafeHandle hPrinter, IntPtr pBuf, int cdBuf, out int pcWritten);

[DllImport("winspool.drv", CharSet=CharSet.Auto, SetLastError=true)]
private static extern int StartDocPrinter(SafeHandles.PrinterSafeHandle hPrinter, int Level, [In] ref DOC_INFO_1 pDocInfo);

[DllImport("winspool.drv", CharSet=CharSet.Auto, SetLastError=true)]
private static extern bool EndDocPrinter (SafeHandles.PrinterSafeHandle hPrinter);

[DllImport("winspool.drv", CharSet=CharSet.Auto, SetLastError=true)]
private static extern bool SetJob (SafeHandles.PrinterSafeHandle hPrinter, int JobID, int Level, IntPtr pJob, int Command);

private const int JOB_CONTROL_PAUSE = 1;
private const int JOB_CONTROL_DELETE = 5;

[StructLayout(LayoutKind.Sequential)]
private struct DOC_INFO_1
{
    [MarshalAs(UnmanagedType.LPTStr)] public string pDocName;
    [MarshalAs(UnmanagedType.LPTStr)] public string pOutputFile;
    [MarshalAs(UnmanagedType.LPTStr)] public string pDatatype;
}


public static int SendPrinterCommand(string PrinterName, string DocumentName, string Command, bool Suspended = false)
{
    return SendPrinterCommand(null, PrinterName, DocumentName, Command, Suspended);
}

public static int SendPrinterCommand(string PrinterName, string DocumentName, string Command, System.Text.Encoding Encoding, bool Suspended = false)
{
    return SendPrinterCommand(null, PrinterName, DocumentName, Command, Encoding, Suspended);
}

public static int SendPrinterCommand(string PrinterName, string DocumentName, byte[] Command, bool Suspended = false)
{
    return SendPrinterCommand(null, PrinterName, DocumentName, Command, Suspended);
}

public static int SendPrinterCommand(string ServerName, string PrinterName, string DocumentName, string Command, bool Suspended = false) 
{
    return SendPrinterCommand(ServerName, PrinterName, DocumentName, Command, System.Text.Encoding.ASCII, Suspended);
}

public static int SendPrinterCommand(string ServerName, string PrinterName, string DocumentName, string Command, System.Text.Encoding Encoding, bool Suspended = false)
{
    return SendPrinterCommand(ServerName, PrinterName, DocumentName, Encoding.GetBytes(Command), Suspended);
}

public static int SendPrinterCommand(string ServerName, string PrinterName, string DocumentName, byte[] Command, bool Suspended = false)
{
    string FullPrinterPath = string.IsNullOrEmpty(ServerName) ? PrinterName : System.IO.Path.Combine(ServerName, PrinterName);

    using (var h = new SafeHandles.PrinterSafeHandle(FullPrinterPath))
    {
        var di1 = new DOC_INFO_1()
        {
            pDocName = DocumentName,
            pOutputFile = null,
            pDatatype = "RAW"
        };

        int job_id = StartDocPrinter(h, 1, ref di1);
        if (job_id == 0)
        {
            throw new System.ComponentModel.Win32Exception();
        }

        if (Suspended)
        {
            if (!SetJob(h, job_id, 0, IntPtr.Zero, JOB_CONTROL_PAUSE))
            {
                throw new System.ComponentModel.Win32Exception();
            }
        }

        try
        {
            int total_bytes_written = 0;

            if (!WritePrinter(h, Command, Command.Length, out total_bytes_written))
            {
                throw new System.ComponentModel.Win32Exception();
            }

            if (total_bytes_written < Command.Length)
            {
                var gch = GCHandle.Alloc(Command, GCHandleType.Pinned);

                try
                {
                    do
                    {
                        int next_index = total_bytes_written;
                        int next_requred_len = Command.Length - next_index;
                        int bytes_written_this_time = 0;

                        if (!WritePrinter(h, Marshal.UnsafeAddrOfPinnedArrayElement(Command, next_index), next_requred_len, out bytes_written_this_time))
                        {
                            throw new System.ComponentModel.Win32Exception();
                        }

                        total_bytes_written += bytes_written_this_time;
                    } while (total_bytes_written < Command.Length);
                }
                finally
                {
                    gch.Free();
                }
            }
        }
        catch
        {
            SetJob(h, job_id, 0, IntPtr.Zero, JOB_CONTROL_DELETE);
            throw;
        }
        finally
        {
            EndDocPrinter(h);
        }

        return job_id;
    }

}

string s = "I8,A,001\n\n\nQ0001,0\nq831\nrN\nS5\nD10\nZT\nJF\nO\nR20,0\nf100\nN\nB775,188,2,1,2,6,160,B,\"SM00020000\",199,1,0,200\nP1\n";

SendPrinterCommand("ZDesigner GT800 (EPL)", "Foo", s);

I would suggest not reinventing the wheel. Take a look at third-party libraries that already do this. For example, ThermalLabel SDK. It's a paid library, but it does well. You might even find some free/open-source ones out there as well.

If any of these does not work, you can write your zpl commands into a file using c# and directly copy it to the printer, if it is shared in network.

    public void Print(int numCopies = 1)
    {

        int randomInt = (new Random()).Next(1000); //this random value is intented to get the collision change of prn file names reduced 
        string SERVERPATH = Path.Combine(System.Web.HttpContext.Current.Server.MapPath("~/PrintOperations/"));

        if (!Directory.Exists(SERVERPATH))
        {
            Directory.CreateDirectory(SERVERPATH);

        }
        String prnFilePath = SERVERPATH + MethodName + randomInt + ".prn";
        String fullPrinterPath = @"\\"+ServerName+@"\"+ printerName;
        var createdFile = System.IO.File.Create(prnFilePath);
        createdFile.Close();
        System.IO.File.WriteAllText(prnFilePath, parsedZpl);
        System.Diagnostics.Process process = new System.Diagnostics.Process();
        System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
        startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
        startInfo.FileName = "cmd.exe";
        startInfo.Arguments = string.Format("/C Copy \"{0}\" \"{1}\"", prnFilePath ,fullPrinterPath);
        process.StartInfo = startInfo;
        for (int i =0; i< numCopies; i++)
        {
            process.Start();
            process.WaitForExit();

        }

        System.IO.File.Delete(prnFilePath);
}