Can't get OpenPrinter to work

[mutlyp]

I am using this code which I got off the net.
I am trying to send a txt file to an Intermec PM4i label printer that takes RAW data and prints out labels. I have loaded the driver and have set up the printer on the machine. I can go into Printers and Faxes select the printer and go into the properties and send a file to the printer and it will print out the labels. So I know it works. But when I run this code it starts off with a dialog box asking for the txt file. Once file is chosen another dialog box opens where you chose the printer. All that seems to work correctly. But when the code goes into the SendBytesToPrinter() Function and gets to OpenPrinter(szPrinterName.Normalize(), hPrinter, IntPtr.Zero) the szPrinterName.Normalize() has the correct printer name.
hPrinter and IntPtr.Zero both has values of Zero.
From this line it goes directly to
If bSuccess = False Then
dwError = Marshal.GetLastWin32Error()
End If
And Marshal.GetLastWin32Error() has a value of 87.
And that’s it and nothing is printed.
Please let me know what is going on?
Thank you

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Windows.Forms
Imports System.Drawing.Printing
Imports System.Runtime.InteropServices
Imports System.IO
Public Class Form1
    ' Structure and API declarions:
    <StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Ansi)> _
    Public Class DOCINFOA
        <MarshalAs(UnmanagedType.LPStr)> _
        Public pDocName As String
        <MarshalAs(UnmanagedType.LPStr)> _
        Public pOutputFile As String
        <MarshalAs(UnmanagedType.LPStr)> _
        Public pDataType As String
    End Class
    <DllImport("winspool.Drv", EntryPoint:="OpenPrinterA", SetLastError:=True, CharSet:=CharSet.Ansi, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
    Public Shared Function OpenPrinter(<MarshalAs(UnmanagedType.LPStr)> ByVal szPrinter As String, ByVal hPrinter As IntPtr, ByVal pd As IntPtr) As Boolean
    End Function
    <DllImport("winspool.Drv", EntryPoint:="ClosePrinter", SetLastError:=True, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
    Public Shared Function ClosePrinter(ByVal hPrinter As IntPtr) As Boolean
    End Function
    <DllImport("winspool.Drv", EntryPoint:="StartDocPrinterA", SetLastError:=True, CharSet:=CharSet.Ansi, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
    Public Shared Function StartDocPrinter(ByVal hPrinter As IntPtr, ByVal level As Int32, <[In](), MarshalAs(UnmanagedType.LPStruct)> ByVal di As DOCINFOA) As Boolean
    End Function
    <DllImport("winspool.Drv", EntryPoint:="EndDocPrinter", SetLastError:=True, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
    Public Shared Function EndDocPrinter(ByVal hPrinter As IntPtr) As Boolean
    End Function
    <DllImport("winspool.Drv", EntryPoint:="StartPagePrinter", SetLastError:=True, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
    Public Shared Function StartPagePrinter(ByVal hPrinter As IntPtr) As Boolean
    End Function
    <DllImport("winspool.Drv", EntryPoint:="EndPagePrinter", SetLastError:=True, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
    Public Shared Function EndPagePrinter(ByVal hPrinter As IntPtr) As Boolean
    End Function
    <DllImport("winspool.Drv", EntryPoint:="WritePrinter", SetLastError:=True, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
    Public Shared Function WritePrinter(ByVal hPrinter As IntPtr, ByVal pBytes As IntPtr, ByVal dwCount As Int32, ByVal dwWritten As Int32) As Boolean
    End Function
    ' 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 Shared Function SendBytesToPrinter(ByVal szPrinterName As String, ByVal pBytes As IntPtr, ByVal dwCount As Int32) As Boolean
        Dim dwError As Int32 = 0, dwWritten As Int32 = 0
        Dim hPrinter As New IntPtr(0)
        Dim di As New DOCINFOA()
        Dim bSuccess As Boolean = False
        ' Assume failure unless you specifically succeed.
        di.pDocName = "My C#.NET RAW Document"
        di.pDataType = "RAW"
        Try
            ' Open the printer.
            If OpenPrinter(szPrinterName.Normalize(), hPrinter, IntPtr.Zero) Then
                ' Start a document.
                If StartDocPrinter(hPrinter, 1, di) Then
                    ' Start a page.
                    If StartPagePrinter(hPrinter) Then
                        ' Write your bytes.
                        bSuccess = WritePrinter(hPrinter, pBytes, dwCount, dwWritten)
                        EndPagePrinter(hPrinter)
                    End If
                    EndDocPrinter(hPrinter)
                End If
                ClosePrinter(hPrinter)
            End If
        Catch ex As Exception
            MsgBox("error")
        End Try
        ' If you did not succeed, GetLastError may give more information
        ' about why not.
        If bSuccess = False Then
            dwError = Marshal.GetLastWin32Error()
        End If
        Return bSuccess
    End Function
    Public Shared Function SendFileToPrinter(ByVal szPrinterName As String, ByVal szFileName As String) As Boolean
        ' Open the file.
        Dim fs As New FileStream(szFileName, FileMode.Open)
        ' Create a BinaryReader on the file.
        Dim br As New BinaryReader(fs)
        ' Dim an array of bytes big enough to hold the file's contents.
        Dim bytes As [Byte]() = New [Byte](fs.Length - 1) {}
        Dim bSuccess As Boolean = False
        ' Your unmanaged pointer.
        Dim pUnmanagedBytes As New IntPtr(0)
        Dim nLength As Integer
        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
    End Function
    Public Shared Function SendStringToPrinter(ByVal szPrinterName As String, ByVal szString As String) As Boolean
        Dim pBytes As IntPtr
        Dim dwCount As Int32
        ' How many characters are in the string?
        dwCount = szString.Length
        ' 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
    End Function
 
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If True Then
            ' Allow the user to select a file.
            Dim ofd As New OpenFileDialog()
            If DialogResult.OK = ofd.ShowDialog(Me) Then
                ' Allow the user to select a printer.
                Dim pd As New PrintDialog()
                pd.PrinterSettings = New PrinterSettings()
                If DialogResult.OK = pd.ShowDialog(Me) Then
                    ' Print the file to the printer.
                    SendFileToPrinter(pd.PrinterSettings.PrinterName, ofd.FileName)
                End If
            End If
        End If
    End Sub
End Class