How to reprint a spool file using XPS printer?

Question

I am building a program to capture printed documents and then convert these documents to xps\image.

Currently i am using FileSystemWatcher to monitor the directory "C:\Windows\System32\spool\PRINTERS\" and copy the spl files, make sure its not duplicate then try converting it to xps file by printing the spl file using the Win32 Spooler API and the Microsoft XPS Document Writer predefined printer, but when i specify an output file as shown below, the error code 1804 is returned, if i leave it empty it succeeds but then i don't get an output file.

    public static bool SendBytesToPrinter(string szPrinterName, IntPtr pBytes, Int32 dwCount, string outputFile, string dataType, out int errorCode)
    {
        IntPtr hPrinter;
        var di = new DOCINFOA();
        var bSuccess = false; // Assume failure unless you specifically succeed.

        di.pDocName = "Spool Doc";
        di.pDataType = dataType;
        di.pOutputFile = outputFile;

        // 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.
                    var dwWritten = 0;
                    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.
        errorCode = bSuccess == false ? Marshal.GetLastWin32Error() : 0;
        return bSuccess;
    }

So, what i am doing wrong, and how to print\convert the spool file to an XPS document, and if possible to an image file and a text file.

Edit: Adding Additional info

here is the implementation of DOCINFOA

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    public class DOCINFOA
    {
        [MarshalAs(UnmanagedType.LPStr)]
        public string pDataType;
        [MarshalAs(UnmanagedType.LPStr)]
        public string pDocName;
        [MarshalAs(UnmanagedType.LPStr)]
        public string pOutputFile;
    }

and here is the complete call chain:

The app runs the following code

    var dataTypes = new[] { null, "RAW", "RAW [FF appended]", "RAW [FF auto]", "NT EMF 1.003", "NT EMF 1.006", "NT EMF 1.007", "NT EMF 1.008", "TEXT", "XPS_PASS", "XPS2GDI" };
    foreach (var dataType in dataTypes)
    {
        int errorCode;
        RawPrinterHelper.SendFileToPrinter(@"Microsoft XPS Document Writer", sourceFile, outputFile, dataType, out errorCode);
        //print errorCode
    }

And in RawPrinterHelper

    public static bool SendFileToPrinter(string szPrinterName, string szFileName, string outputPath, string dataType, out int errorCode)
    {
        // Open the file.
        var fs = new FileStream(szFileName, FileMode.Open);
        // Create a BinaryReader on the file.
        var br = new BinaryReader(fs);
        // Dim an array of bytes big enough to hold the file's contents.
        // Your unmanaged pointer.
        var documentPath = Path.GetFileName(szFileName);
        var nLength = Convert.ToInt32(fs.Length);
        // Read the contents of the file into the array.
        var bytes = br.ReadBytes(nLength);
        // Allocate some unmanaged memory for those bytes.
        var 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.
        var bSuccess = SendBytesToPrinter(szPrinterName, pUnmanagedBytes, nLength, outputPath, dataType, out errorCode);
        // Free the unmanaged memory that you allocated earlier.
        Marshal.FreeCoTaskMem(pUnmanagedBytes);
        fs.Close();
        return bSuccess;
    }

And the API functions

    [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, Int32 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, Int32 dwCount, out Int32 dwWritten);

Answer 1

The problem is your declaration of the DOC_INFO_1 struct. It doesn't match the layout Windows expects. The Windows declaration looks like this:

typedef struct _DOC_INFO_1 {
  LPTSTR pDocName;
  LPTSTR pOutputFile;
  LPTSTR pDatatype;
} DOC_INFO_1;

But your declaration has it like this:

public class DOCINFOA
{
    public string pDataType;
    public string pDocName;
    public string pOutputFile;
}

Reorder the elements in your declaration to match the Windows struct and it should fix your problem.

EDIT: Bad news. Your approach will not work. Take a look at the documentation for WritePrinter:

WritePrinter only supports GDI printing and must not be used for XPS printing. If your print job uses the XPS or the OpenXPS print path, then use the XPS Print API. Sending XPS or OpenXPS print jobs to the spooler using WritePrinter is not supported and can result in undetermined results.