I'm trying to print extended code page 850 characters using ZPL II to a Zebra S4M. Whenever one of the extended characters I.E. ASCII value > 127 is used I get a box of varying shades of grey instead of the actual value.

I'm trying to print ± and ° (ALT+0177 and ALT+0176). I suspect its the RawPrinterHelper I am trying to use (as downloaded from MS, and another from CodeProject) however I cant see where the character codes are going wrong.

Weirdly, printing direct from Notepad renders the correct characters, which leads me to believe it is a problem with the raw printer helper class.

I am not tied to using the Raw Printer Helper class so if there is a better way of doing it, I am more than happy to see them.

SAMPLE ZPLII Without escaped chars

^XA
^FO30,200^AD^FH,18,10^FD35 ± 2 ° ^FS
^FS
^XZ

With escaped chars (tried both upper and lower case)

^XA
^FO30,200^AD^FH,18,10^FD35 _b0 2 _b1 ^FS
^FS
^XZ

Raw Printer Helper

[StructLayout(LayoutKind.Sequential)]
public struct DOCINFO
{
    [MarshalAs(UnmanagedType.LPWStr)]
    public string printerDocumentName;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string pOutputFile;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string printerDocumentDataType;
}

public class RawPrinter
{
    [
        DllImport("winspool.drv", CharSet = CharSet.Unicode, ExactSpelling = false,
            CallingConvention = CallingConvention.StdCall)]
    public static extern long OpenPrinter(string pPrinterName, ref IntPtr phPrinter, int pDefault);

    [
        DllImport("winspool.drv", CharSet = CharSet.Unicode, ExactSpelling = false,
            CallingConvention = CallingConvention.StdCall)]
    public static extern long StartDocPrinter(IntPtr hPrinter, int Level, ref DOCINFO pDocInfo);

    [
        DllImport("winspool.drv", CharSet = CharSet.Unicode, ExactSpelling = true,
            CallingConvention = CallingConvention.StdCall)]
    public static extern long StartPagePrinter(IntPtr hPrinter);

    [
        DllImport("winspool.drv", CharSet = CharSet.Ansi, ExactSpelling = true,
            CallingConvention = CallingConvention.StdCall)]
    public static extern long WritePrinter(IntPtr hPrinter, string data, int buf, ref int pcWritten);

    [
        DllImport("winspool.drv", CharSet = CharSet.Unicode, ExactSpelling = true,
            CallingConvention = CallingConvention.StdCall)]
    public static extern long EndPagePrinter(IntPtr hPrinter);

    [
        DllImport("winspool.drv", CharSet = CharSet.Unicode, ExactSpelling = true,
            CallingConvention = CallingConvention.StdCall)]
    public static extern long EndDocPrinter(IntPtr hPrinter);

    [
        DllImport("winspool.drv", CharSet = CharSet.Unicode, ExactSpelling = true,
            CallingConvention = CallingConvention.StdCall)]
    public static extern long ClosePrinter(IntPtr hPrinter);

    public static void SendToPrinter(string printerJobName, string rawStringToSendToThePrinter,
                                     string printerNameAsDescribedByPrintManager)
    {
        IntPtr handleForTheOpenPrinter = new IntPtr();
        DOCINFO documentInformation = new DOCINFO();
        int printerBytesWritten = 0;
        documentInformation.printerDocumentName = printerJobName;
        documentInformation.printerDocumentDataType = "RAW";
        OpenPrinter(printerNameAsDescribedByPrintManager, ref handleForTheOpenPrinter, 0);
        StartDocPrinter(handleForTheOpenPrinter, 1, ref documentInformation);
        StartPagePrinter(handleForTheOpenPrinter);
        WritePrinter(handleForTheOpenPrinter, rawStringToSendToThePrinter, rawStringToSendToThePrinter.Length,
                     ref printerBytesWritten);
        EndPagePrinter(handleForTheOpenPrinter);
        EndDocPrinter(handleForTheOpenPrinter);
        ClosePrinter(handleForTheOpenPrinter);
    }
}